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COPYRIGHT DEPOSm 



AN 



ELEMENTARY PHYSIOLOGY 
AND HYGIENE 



FOR USE IN SCHOOLS 



BY 

H/W; CONN, Ph.D. 

PROFESSOR OF BIOLOGY IN WESLEYAN UNIVERSITY 




» ' © B » ., 



SILVER, BURDETT AND COMPANY 

NEW YORK BOSTON CHICAGO 



THE LIBRARY OF 
CONGRESS. 

Two Copies Received 

MAY 27 1903 

Copyright Entry 

CLAS5 ^ XXc No. 

COPY 8. 



COPTEIGHT, 1903, 

By silver, BUEDETT AND COMPANY. 



PREFACE 

The aim of the author in writing the present work 
has been to furnish an elementary text-book in physi- 
ology and hygiene which should recognize some of the 
more important discoveries of recent years concerning 
matters pertaining to health, and which should also 
attempt to exemplify in the clearest way the inter- 
relation between physiology and hygiene. 

The primary object of the study of physiology in our 
schools is to inculcate an intelligent care of the body. 
With this in view, matters of hygiene must in one 
sense take first place, although our understanding of 
hygiene must always be based upon a knowledge of 
physiology. In the present work the study of the 
body, and of its various parts and their functions, is 
given full and comprehensive treatment ; at the same 
time lessons on hygiene are given as natural results 
of the principles of physiology and as closely related 
thereto. 

The chapters upon foods and their values and tlie 
treatment of the causes and distribution of contagious 
and other germ diseases are included from the belief 
that these new lines of discovery are of such vital 
importance that they should be a part of the knowl- 
edge of every boy and girl. 

The effect of alcohol upon the various functions of 
the body is treated throughout the book in direct rela- 

3 



4 PREFACE 

tion with the particular organs or functions concerned. 
In this Avay, it is believed, the facts will be most clearly 
and usefully apprehended. The dangers connected 
with the use of alcohol will be found plainly indicated, 
and the statements, it is believed, are strictly in accord 
with the results of the latest investigations in that 
department of science. 

The author desires to express his hearty acknowledg- 
ments to Superintendent W. P. Ferguson of Middle- 
town and Dr. George W. Fitz of Boston for their 
kindness in looking over the proofs of the work and 
giving him the benefit of their criticisms. He wishes 
also to express his obligations to Professor W. O. At- 
water. Professor William N. Rice, and Dr. F. G. Bene- 
dict of Wesleyan University, to Professor C. F. Hodges 
of Clark University, to the Rev. J. H. James, President 
of the Connecticut Temperance Union, and to Superin- 
tendent J. G. Edgerly of Fitchburg, Massachusetts, for 
their valuable suggestions. While acknowledging ob- 
ligations to these gentlemen, it is not implied that any 
of them can be held responsible for the method of 
treatment in the work or as necessarily indorsing it 
or any part of it. 

The expression of the author's thanks is also due to 
many teachers who have aided him by valuable sugges- 
tions arising from their practical experience. 

•MiDDLETOWN, CONNECTICUT, 

April, 1903. 



CONTENTS 



CHAPTER 
I. 



Foods and Food Materials . 

Purposes of Food Alcohol 



11-36 



Kinds of Food 
Sources of Food 
Other Food Material 

II. Digestion . 

The Mouth 

Food in the Mouth 

Throat 
Food in the Stomach 
Food in the Intestines 



Amount of Food Needed 
Comparative Food Values 



37-64 

Digestibility of Foods 
and How the Food gets into 

the Blood 
Undigested Portions of 

the Food 



III. Food Habits and Cooking .... 
Proper Habits of Eating Purposes of Cooking 
The Habit of using Alco- Principles of Cooking 
hoi Methods of Cookino- 



65-79 



IV. Circulation 
The Blood 
What makes the Blood 

Flow 
Blood Vessels 
How the Blood Flows 

V. Respiration 

The Air Passages and the 

Lungs 
How Air is drawn into 

the Luno's 



80-103 

How the Flow of Blood is 

Controlled 
Summary of the Circula- 
tion Process 

101-1-23 

What Breatiiing does for 

the Blood 
Ventihition 
How to restore Respiration 



6 CONTENTS 

CHAPTER PAGE 

VI. The Framework and Motion of the Body 124-152 

The Skeleton Joints 

The Bones The Muscles 

Cartilage 

VII. The Kidneys and the Skin and their Duties 153-171 

Waste Products The Skin 

The Kidneys Functions of the Skin 

VIII. The Care of the Skin 172-179 

Bathing Burns 

Clothing Frostbites 

IX. Stimulants and Narcotics .... 180-188 

Opium Alcohol 

Tobacco 

X. The Nervous System 189-197 

The Brain The Nerves 

The Spinal Cord 

XL The Nervous System in Action . . . 198-212 
Duties of the Nerves The Cerebellum and Cerebrum 

Duties of the Spinal Cord The Importance of Habits 
and Medulla The Care of the Mind 



XII. 


The Senses 


213-236 




The Sense of Sight 


The Sense of Smell 




The Sense of Sound 


Skin Sensations 




The Sense of Taste 




XIII. 


Health and Disease 


237-251 




Parasitic Diseases 


The Duty of preserving 




The Use of Alcohol 


Health 


XIV. 


What to do in Emergencies .... 252 


Glossary .... 


257 


Index 




265 



ILLUSTRATIONS 



FIG. PAGE 

1. Starch Grains . . . .- " 16 

2. Fat Cells 17 

3. A Small Bit of a Grain of Wheat 21 

4. TPie Oat Plant 22 

5. A Small Bit of Potato 23 

6. Yeast Plant . . .27 

7. Sugar Solution undergoing Fermentation by Yeast . 28 

8. Showing the Proportion of Alcohol and Water in Beer, 

Wine, and Whisky 29 

9. The Upper Teeth 39 

10. The Mouth 40 

11. A Diagram of the Side of the Face 41 

12. A Section through the Head 44 

13. The Digestive Organs of the Abdomen .... 47 

14. A Section of the AYall of the Stomach .... 48 

15. Showing the Location of the Digestive Organs . . 50 

16. A Bit of the Intestine 58 

17. A Bit of the Intestine 59 

18. A Single Villus . . .60 

19. A Simple Device for showing how Foods may pass 

through Membranes ... ... 61 

20. A Little Blood as it appears under a Microscope . . 81 

21. The Heart 83 

22. A. The Chief Arteries and Veins. B. Showing the 

Entrance of the Chief Veins into the Heart facing 84 

23. The Right Side of tlie Heart . . . . \ . 84 

24. The Left Side of the Heart 84 

25. Capillaries 88 

26. Diagram showing General Circulation . . . .89 

27. Showing Main Artery of the Arm 91 

7 



ILLUSTRATIONS 



facing 
facing 



PAGE 
91 

92 

93 

94 

98 

107 

108 

108 

108 

109 

110 

111 

119 



28. Showing Main Artery in the Leg .... 

29. Showing how to compress the Arm to stop Bleeding 

30. Showing the Method of applying a Ligature 

31. Showing the Clotting of Blood 

32. Section of an Artery and a Vein 

33. The Lungs .... 
31. Air Sacs 

35. The Air Sac of the Lungs 

36. Muscle Fibers .... 

37. Showing Chest with Lungs and Heart behind the Kibs 

38. Showing Movement of the Diaphragm in Breathing 

39. Showing Movement of the Ribs in Breathing . 

40. Ventilation ........ 

41. The INIethod of Moving the Arms to produce Artificial 

Breathing 121 

42. The Human Skeleton 125 

43. Two Vertebrae in Position ...... 126 

44. The Human Skull 127 

45. A Section of the Femur 128 

46. The Cramped Foot 130 

47. The Uncramped Foot 130 

48. An Improperly Shaped Shoe 131 

49. The Properly Shaped Shoe 131 

50. Two Vertebrae 133 

51. The Bones forming the Knee Joint . . . r . 135 

52. The Knee Joint 136 

53. The Bones of the Shoulder Joint 138 

54. The Shoulder Joint 139 

55. Showing Method of Attachment of Biceps Muscle to 

move the Forearm .... 

56. Showing Muscles and Tendons of the Arm 

57. A Bit of Muscle 

58. A Bit of Muscle . . . . 

59. The Surface Muscles of the Body 

60. The Kidneys 155 

61. A Section of a Bit of Skin 157 

62. A Hair 159 

63. A Section through the Tip of the Finger . . . 161 



141 
142 
143 
143 
147 



ILLUSTRATIONS 9 

FIG. PAGE 

64. A Bit of Skin as it appears under a Microscope . . 164 

65. The Human Brain . . . . . . . .190 

6Q. The Nervous System 192 

67. Two Pieces of the Spinal Cord 193 

68. A Nerve 195 

69. A Nerve Cell " . .196 

70. Showing Connection of Hand with Brain by a Nerve . 199 

71. The Brain in Position 206 

72. The Eye, viewed from in Front 214 

73. The Eye, viewed from the Side 216 

74. A Comparison of the Structure of a Camera and the Eye 217 

75. A Diagram representing a Section through the Human 

Eye .218 

76. The Ear 222 

77. The Tongue .... 227 

78. A Vertical Section of the Nose 230 



PHYSIOLOGY AND HYGIENE 

CHAPTER I 
FOODS AND FOOD MATERIALS 

OuK bodies are in some respects like an engine 
that is constantly at work. As an engine is cold and 
powerless without fuel, so our bodies without food 
would starve and die. As the engine usually works 
smoothly and strongly, so the body, when we are in 
good health, is strong and active. But sometimes the 
body, like the engine, breaks down in part, and cannot 
do all its work. Then we say that we are ill. Smooth 
action of the engine means good health. When any- 
thing interferes with its working properly, sickness 
results. If the machine stops entirely, we say there is 
death. Physiology teaches us about the body, what 
the work of each part is; and Hygiene teaches us how we 
may treat the body wisely, just as the skillful engineer 
cares for his engine in tlie best possible way. 

PURPOSES OF FOOD 

When we speak of food, we ordinarily mean materials 
suitable for us to eat. In this chapter we shall include 
in the word ^^food," only the portion of the food 

11 



12 PHYSIOLOGY AXD HYGIENE 

material that can be taken into the blood, and so give 
nourishment to the body, and not that which passes 
out as waste. 

In order that an engine may be kept running, it is 
necessary, of course, that coal or other fuel be regularly 
supplied, so that the engine may continue to have heat 
under its boilers, and power to run. But the coal 
could not keep the wheels revolving if an important 
part of the engine should break down. The care of 
the engine, then, includes also the repairing or re- 
placing of parts that break or wear out. In much 
the same w^ay our bodies need not only heat and 
energy, but also the constant building and repair of 
parts which are used up from day to day. Our food 
supplies us w^ith material for building and repair, as 
well as for heat and energy. 

Foods for Building and Repair. — When you say, 
" I have grown two inches since last year," you mean 
that your bones and muscles have increased in size a 
certain amount during the last twelve months. Even 
after we have reached our full height, certain parts of 
the body still continue to grow. The hair and finger 
nails need frequent cutting, and the skin is all the 
time wearing away. Although we cannot see so 
readily that the bones and muscles w^ear out and 
require constant repair, it is equally true. It is neces- 
sary, then, that our bodies receive in food some building 
material which can be used to increase the size of 
growing muscles and bones, and to replace those parts 
that are worn out. 



FOODS AND FOOD MATERIALS 13 

Foods for Fuel. . — In addition to the material used 
for building and repair, our bodies need food that will 
serve as fuel, like the coal on the steamship, to supply 
heat, and power to use the muscles. Although we may 
feel so cold that our bodies fairly ache, as we say, still, 
as long as our hearts beat, that is, as long as we live, our 
bodies are always warm. If you look at a thermom- 
eter, you will see that a certain point on the scale 
is marked ""^ blood heat." This means that the point 
marked 98° is about the normal temperature of the blood. 
If the blood is cooler than this, we are ill; even a de- 
gree or two of additional heat in the body is fever. As 
we shall learn in a later chapter, our bodies are kept 
at the proper temperature by using up certain food 
materials, much as a stove or heater is warmed by the 
burning of coal. The flame which we see when wood 
or coal is burned is caused by the uniting of the fuel 
with a gas in the air which is called oxygen. In a 
similar way, but without flame, the heat-giving foods 
which we eat combine inlbur bodies with the oxj^gen 
which has been taken in with the air we breathe. 

KINDS OF FOOD 

The kinds of food which people eat appear to be 
numerous. As we study them carefully, however, we 
find that although our dinner table may hold a number 
of delicious things, the different articles of food are 
made up of a very few substances. Some of these 
substances, of which we shall learn more very soon, 
furnish our bodies with both buildinof material and 
fuel, others chiefly with fuel. 



14 PHYSIOLOGY AND HYGIENE 

Let us now consider these special food substances 
which are contained in the things we eat. 

Foods used for both Fuel and Repair. Albumen. — If 
we break an egg carefully, we can separate the white 
from the yolk. Tliis white, transparent, jellylike sub- 
stance is known as albumen, and is a valuable food 
substance. The white of the egg is one of the purest 
forms of albumen, but though we cannot see it so 
readily, albumen is found in meat, milk, and other 
articles of food. If you heat the white of the egg^ it 
becomes solid, undergoing a change called coagulation. 

Myosin. — The lean part of meat after the gristle has 
been removed is another important food substance, and 
is called myosin. Uncooked myosin is soft and elas- 
tic ; but cooking coagulates it, just as boiling hardens 
the white of the egg. 

Gluten. — If we Avrap a little flour in a piece of fine 
muslin and allow water to run through it, most of the 
flour will be washed away. A sticky, gummy, white 
mass will be left. This is gluten. 

Casein. — Milk contains a food substance called 
casein. If we pour a little weak acid, like vinegar, 
into the milk, the latter curdles. The curd, or thick 
whitish substance, is casein. When pressed into cakes 
and dried in a certain way, it becomes cheese. 

These foods, albumen^ myosin^ gluten^ and casein^ build 
up the body, help to keep it in repair, and serve also as 
fuel. Thej^ are called proteids, or nitrogenous foods, 
and without them the body would starve. It must 
not be supposed, however, that eggs, meat, flour, and 



FOODS AND FOOD MATEPJALS 15 

milk are the only proteid foods, since there is some 
proteid in almost all classes of foods. Peas, beans, 
lentils, and similar v-egetables are very rich in pro- 
teids, and are for millions of people the cheapest and 
most convenient of proteid foods. 

Foods used chiefly for Fuel. — A man might have the 
muscles of a Samson, but if he were unable to lift 
anything with his sinewy arm, or to run upon his well- 
built legs, he would be of no more use to the Avorld 
than a statue. To enable us to use our muscles we 
need more than the building and repairing foods ; we 
must give our bodies something that will supply 
warmth and muscular power. The proteids or building 
foods may be used partly for this purpose, but we have 
in addition three important food substances that act 
mainly as fuels, — starch, sugar, and fats. They furnish 
us with heat and the power necessary for motion. 
Although our diet cannot be confined to either class, 
we really need a larger amount of the fuel foods than 
of the proteids. 

Starch. — Starch is found in certain of our vegetable 
foods, such as flour, oats, and potatoes. For use in 
the laundry and as stiffening for puddings, the starch 
is separated from the other substances found in pota- 
toes and corn ; we then call it either laundry starch 
or corn starch. We must remember, however, tliat 
starch is really present in every potato, every kernel 
of corn, and every grain of wheat. We can easily see 
whether starch is contained in a fruit or a vegetable 
by touching it with a drop of water containing a little 



16 



PHYSIOLOGY AND HYGIENE 




iodine. 1 If there is starch in the vegetable, the spot 
touched will turn blue. The starch always appears 
in the form of very minute grains. Figure 1 shows 
starch grains as they look when seen through a power- 
ful microscope. 

We can cook our starch by putting a little into 
water and boiling it. The heat swells the grains of 

starch and the mass becomes a 
thick paste. 

Sugar. — Sugar, like starch, is 
a fuel food, although in appear- 
ance and taste the two differ 
widely. There are several 
kinds, the so-called cane sugar^ 
made from sugar cane, being one 
of the sweetest. Beet sugar^ 
manufactured from the sugar 
beet, is also of excellent quality. Grlucose or grape 
sugar^ which is found in fruits and in corn, is less 
sweet than cane or beet sugar, but as it is more cheaply 
prepared for market, it is often used for adulterating 
other sugars. Milk contains a kind of sugar known 
as milk sugar. All sugars are of about equal value as 
foods, despite their different degrees of sweetness. 

We can readily observe a difference between sugar 
and starch by placing a little sugar in water and heat- 
ing gently, and then repeating the experiment with 
starch. The sugar quickly dissolves, while the starch 

1 A few drops of tincture of iodine in a teaspoonful of water is 
sufficient for a number of tests. 



Fig. 1. — Starch Grains, 

As seen through a 

microscope. 



FOODS AND FOOD MATERIALS 17 

does not, but, as we have already seen, swells if the heat 
is sufficient. 

Starch and sugar, though so different in some re- 
spects, are closely related and have much in common. 
Starch is changed to sugar in fruits as they ripen, in 
seeds and bulbs as they grow, and the same process 
takes place in our starchy foods as they are digested. 

Fats. — Fats are among the very best fuel foods. It 
is because of its excellent heat-giving qualities that 
the Eskimos eat so much of the blubber or fat of seals 
and other animals ; the fat enables them to endure the 
severity of their cold climate. Butter^ tallow^ lard^ olive 
oil^ and cottonseed oil are fats. Some of the fats used as 
foods, such as butter and lard, come from animals ; and 
others, such as olive and cottonseed oils, from the vege- 
table world. Several of the fats, like lard, are solid 
when they come from the market, becoming liquid 
only when subjected to heat ; others, like olive oil, 
are always liquid. 

Animal fat is made up /"""^f iM^l"^^ 

of little drops, each in- 
closed in a sac. The sacs -^^P 
can be seen only with Connect/t/p 
the aid of a microscope. ^^^^ 

Figure 2 shows a group ^^^- 2. -Fat Cells. 

of fat ceXU ^s thev thus ^^ ^^''^^ ''^'^''''' "' ^ ^'^''^ ""^ "^^""^ 
01 lat ceils as tney tnus ^^^^.^^^ ^ microscope. 

appear ; the figure shows 

five fat drops in their sacs, in the form in whicli they 
are found in animal foods, such as a piece of beef- 
steak. We must remember, however, that when we 




18 PHYSIOLOGY AND HYGIENE 

look at animal fat it is solid and white because it is 
cold. In the living animal it is liquid, because of the 
heat of the body, and it is transparent. 

Melted fats or oils, Avhen mixed with certain liquids, 
break up into very small drops, making the liquids 
look white. Tlie millions of minute fat drops in milk 
aid in giving the liquid its white color. 

To test this, place a few drops of olive oil or castor 
oil and some water in a small bottle and shake rapidly. 
Then let it stand for an hour or so and note the change. 

Material for Bone Making. — As we shall see later, 
bones are made up of two widely different materials. 
Part of the bone, what is called the organic matter, is 
made up from the proteids which are so useful in build- 
ing up other parts of the body. The harder mineral 
matter of the bone is lime^ which is contained in small 
quantities in such common foods as meat, bread, milk, 
and eggs. Thus our ordinary food furnishes us with 
all material needed for bone building. 

SOURCES OF FOODS 

Although the substances about which we have just 
been studying are the foods necessary to sustain life, we 
seldom eat any one of them singly or in a pure form. 
Take bread, for example. As usually made, it contains 
flour, milk, sugar, lard, and salt. The flour gives us 
starch and gluten, the milk casein and sugar, the lard 
fat. And so it is with almost everything we eat. 
Usually several food substances are to be found in 
each single article of diet. See tables, pages 33-35. 



FOODS AND FOOD MATERIALS 19 

Foods come both from animals and from plants. The 
principal animal foods are milk, meats, and eggs. 

Milk. — Milk is one of the cheapest and best of foods. 
We may be sure, as it is the natural food for babies, 
that it is easily digested and contains all the materials 
necessary for life, growth, and activity. The curd is 
the hody-huilding food, and the cream, or fat, and the 
milk sugar are the force-producing foods. We sliould 
always remember that milk should be used as a food^ 
and not to take the place of watex' as a drink to quench 
thirst. 

Alilk should usually be the chief food for a child 
until his first teeth appear. When he becomes active 
and begins to walk, milk does not furnish enough 
force-producing material, and this must be obtained 
from starchy foods, such as bread, crackers, and other 
cereal foods. 

The fat or cream may be allowed to rise to the sur- 
face of the milk and can then be taken off and churned 
into butter. The skimmed milk remaining still holds 
most of the sugar and just as much of the building 
food as could be found before the cream was re- 
moved ; therefore it remains a valuable food. Skimmed 
milk contains a little less fuel substance than does 
new milk, but it is equally serviceable for body build- 
ing. It is so cheap that it is a valuable food for those 
who have but little money to spend. The curd, when 
separated from the rest of the milk, is pressed and 
dried to make cheese. Both cheese and butter are very 
useful foods. 



20 PHYSIOLOGY AND HYGIENE 

Danger in Milk. — Since milk is capable of holding 
and transmitting the germs of certain diseases, it is 
sometimes a source of danger. Typhoid fever, diph- 
theria, scarlet fever, and tuberculosis (consumption) 
are occasionally caused by impure milk. Much of the 
illness suffered by babies and little children in warm 
weather may be traced to milk which has been made 
impure by a lack of cleanliness about milkmen, cows, 
barns, milk-houses, or milk-cans. It is necessary that 
milk, and all utensils holding it, should be kept per- 
fectly clean. Some dealers send men to inspect the 
farms from which they obtain milk, to see that every- 
thing about the dairy is kept neat. 

To avoid these dangers, milk should be bought from 
a reliable dealer. It should be kept cold until used, 
and all dishes in which it is to stand should be w^ashed 
with loilmg water before the milk is put into them. 
It is wise also, especially in warm weather, to " scald " 
the milk which is to be used by young • children or 
invalids. This removes much of the possibility of 
danger, and is very little trouble, as the milk needs 
only to be brought to the boiling point (but not boiled) 
and then cooled. Milk that has been boiled is not so 
w^holesome as milk that has merely been ''scalded." 

Meats. — Common meats consist of lean substance, 
or flesh, with some fat and considerable water. The 
flesh (myosin) is one of our most valuable body- 
building foods. So far as the amount of useful food 
is concerned, cheap meats are as nourishing as the 
more expensive cuts. A pound of round steak will 



FOODS AND FOOD MATERIALS 



21 



give us just as much good food as an equal quantity 
of porterhouse steak. The extra money for high-priced 
meat is paid largely because these cuts are more tender 
than the cheaper parts and because the taste is in some 
respects better. 

Eggs. — Albumen and fats are the principal foods 
in eggs. When cooked but a little, whether boiled 
in the shell or dropped into hot water, eggs are health- 
ful and nourishing. Hard-boiled eggs are less easily 
digested, because the juices of the stomach do not act 
readily upon the tough, coagulated mass. When very 
thoroughly chewed, however, they are more readily 
digested. 

Plant Foods. ■ — A large part of our food comes from 
plants. The 
most impor- 
tant of the 
plant foods 
are grains or 
cereals. The 
chief cereals 
eaten in this 
country are 
ivlieat^ oats^ 
rye^ and corn 
(which are 
ground into 

flour, graham meal, oatmeal, rye meal, and Indian meal), 
and rice. In the countries of eastern Asia rice is the 
chief cereal used for food. 




Fig. 3 



5tarch Cdb 

(j/uten 
Cells 

A Small Bit of a Grain of Wheat. 
Highly magnified. 



22 



PHYSIOLOGY AND HYGIENE 



All cereals contain a large proportion of starch, or 
fuel food, and a small amount of the building materials, 
such as gluten. Wheat is one of the best cereals, 
since it has more gluten (that is, more building food) 
than most of the others* Figure 3 shows a small piece 
of a grain of wheat as it appears under the micro- 
scope. Some of the cells, 
as indicated, are loaded 
with starch, and others, 
fewer in number, contain 
gluten. About one eighth 
of our wheat flour is glu- 
ten. Oats (Fig. 4) are 
even better food than 
wheat, containing, as they 
do, a still larger propor- 
tion of gluten, nice fur- 
nishes less building food 
than wheat, but more fuel 
food (starch). Cor^i con- 
tains also considerable fat. 
All of these cereals are 
thus excellent foods. They give us more fuel than 
meat and eggs, but less of the proteids or building foods. 
Wheat bread supplies a good proportion of the necessary 
materials for fuel and repair. A person could keep from 
starvation on a diet of bread and butter alone, but a 
variety of foods is always desirable. Meat and cheese go 
well with cereals, since they furnish the proteid and fat 
elements lacking in the grains. 




EiG. 4. — The Oat Plant. 



FOODS AND FOOD MATERIALS 



23 



Beans and Peas. — As hearts^ peas^ lentils^ and peanuts 
contain large quantities of starch and proteids, they are 
especially nourishing foods. More than one fifth of the 
substance of the bean is proteid, a larger proportion 
than is contained even in meat. Although they are 
not so easily digested as meat, they serve as an excel- 
lent substitute, and they are cheaper. 

Fruits and Vegetables. — Although most fruits and 
vegetables contain little of the real food substances, 
they stimulate the appetite and thus give relish to the 
more substantial foods. They are composed largely of 
water, with a small amount of starch or sugar, flavoring 
matter which makes them pleasant to the taste, and also 
certain salts which aid digestion. 

Some of them, however, such as potatoes, beets, 
bananas, cocoanuts, and nuts, contain sufficient starch, 
proteid, sugar, or fat 
to be valuable as 
foods. Indeed, vege- 
tables and acid fruits 
seem to be needed by 
the body, as sailors 
or explorers, when 
deprived of them, 
suffer from scurvy 
and other diseases. 

Figure 5 represents 
a bit of potato magnified, showing the grains of starch. 
As the potato consists so largel}^ of starch, it is a fuel 
food, and we should eat Avith it meat, milk, cheese, or 




6torch 

Fig. 5. — A Small Bit of Potato. 

Highly magnified. Showing cells filled 

with grains of starch. 



24 PHYSIOLOGY AND HYGIENE 

some other food which will supply proteids for the 
building material which the potato lacks. 

We maj^ eat freely of fruits if they are ripe and per- 
fectly sound, but unripe and overripe fruits are un- 
wholesome and injurious to health. 

OTHER FOOD MATERIAL 

There are certain other substances which we eat or 
drink that are not true foods. Some of them are neces- 
sary to life, some of them are of use, others may be 
harmful. Let us see what some of these are. 

Water. — The shipwrecked sailor who is cast ashore 
on a rocky island or drifts about in an open boat can 
live for many days without food, but without water he 
soon becomes almost crazed with thirst, and in a 
very few days he dies. Our blood, muscles, and vital 
organs all contain water. Without this necessary fluid, 
the foods eaten could not be dissolved and thus made 
ready for transformation into blood and muscle. 

The various other drinks, such as milk, soda water, 
beer, and wine, allay thirst only because of the water 
they contain, and none of them is equal to water itself for 
this purpose. If we quench our thirst with water only, 
we are not so likely to drink too much as we are when 
we attempt to satisfy ourselves with liquids containing 
other material. When we drink something that has 
an especially pleasing taste, the pleasure of taste may 
lead us to drink more than is wise. 

Cool water is one of the most refresliing of drinks on 
a hot day, but extremely cold water, if taken in large 



I 



FOODS AND FOOD MATERIALS 25 

quantities when the body is overheated, may produce a 
shock which is harmful. Ice water or other cold water 
should be drunk very slowly. After violent exercise in 
the hot sun, it is wise to wait for a few minutes before 
drinking cold water. 

Impurities in Water. — It is not easy to find abso- 
lutely pure water. Some of the impurities in drinking 
water are harmless ; others are very injurious. Water 
sometimes contains certain minerals which it gets from 
the earth. These make the water ''hard"; but though 
hard water sometimes produces slight bowel troubles, it 
is not especially harmful. 

The most dangerous impurities in water are minute 
living plants called bacteria. Some of these, as we shall 
notice in a later chapter, may produce disease, if they 
are taken into the body. One kind of bacteria, occa- 
sionally found in drinking water, gives rise to typhoid 
fever. It is impossible to judge either by the appear- 
ance or by the taste, whether water does or does not con- 
tain injurious bacteria. It may be perfectly clear and 
of the finest taste, and yet be unsafe to drink. 

Spring water is almost always pure, if the spring is 
deep and a good distance from anj^ foul place, such as 
an open drain or a barnyard. The lahes and reservoirs 
from which cities obtain water are usuall)^ kept in good 
condition by the authorities ; if at any time the water 
becomes unfit to drink, people are advised to boil it. 
Wells^ particularly if they are on a lower level than the 
houses or barns for which they supply water, are likely 
to contain injurious bacteria. These may either pass 



26 PHYSIOLOGY AND HYGIENE 

down through the soil or drain into the wells from the 
surface. River ivater is usually unfit to drink, especially 
if there are towns or cities on the banks that allow 
sewage to pour into the stream. Such water can be 
made healthful only by boiling. The dangerous bac- 
teria are destroyed by heat. When typhoid fever pre- 
vails, it is always a wise precaution to boil the drinking 
water. 

Mineral Substances. — Several mineral substances, 
called salts^ are needed by the body in small amounts. 
Lime is required to make bone. We eat common salt 
with most of our food. Although salt neither builds up 
the body nor supplies fuel, it is absolutely necessary for 
health. Cattle will eat the grass grown on salt marshes, 
in spite of its coarseness, because they like the salty 
taste. Our ordinary food contains sufficient lime for 
bone material, as well as whatever other salts, aside 
from common salt, the body requires. 

Flavors. — While w^e do not partake of food simply 
because we enjoy eating, still the different articles of 
diet give us a certain pleasure because of their various 
flavors, and indeed some flavor to our foods is neces- 
sary to enable us properly to digest them. The taste 
of puddings, cakes, pies, and similar dishes is due 
largely to certain substances added to give a desired 
flavor. The most common of these flavorings are 
lemon, vanilla, and spices. Tea and coffee are liked 
partly because of their pleasant taste, partly because 
of their slight stimulating effect. Young people are 
better off without them, and taken in excess they are 



FOODS AND FOOD MATEFJALS 27 

injurious to the nerves and the digestion of every one. 

Chocolate, in addition to having a fine flavor, contains 

real food. 

ALCOHOL 

Alcohol is a clear, transparent liquid, in appearance 
resembling water, but very different from water in its 
nature and effects. Although alcohol is found in 
smaller or larger quantities in various materials used 
for drinking purposes, it will neither quench thirst nor 
take the place of water in the body. Pure alcohol has 
a strong odor and an unpleasant taste. 

Although alcohol and water appear so much alike, 
we can test the difference: 1. By smelling them — 
water is odorless, w^hile alcohol has a pungent odor. 
2. By pouring a few drops 
of alcohol and water into 
saucers and applying a 
lighted match — the alco- 
hol burns. 3. By putting 
salt into Avater and also 

into alcohol— upon being ^^^- ^--Y^^^^^ l^^^^^^^- 

Highly magnified. 
shaken gently, the salt 

dissolves in the water, while in tlie alcohol it remains 
undissolved. Similar results are obtained if we sub- 
stitute sugar for salt. 

How Alcohol is made. — Alcohol is made from sugar 
by a process called fermentation. Tlie fermentation is 
bi'ought about by a minute plant called yeast, io be 
seen only with the aid of a microscope. The common 
j'Cast which may be purchased at the grocer}^ store con- 




28 



PHYSIOLOGY AND HYGIENE 



sists of many hundreds of thousands of these tiny plants 
(Fig. 6). If a bit of yeast is placed in a sirup made of 
water and sugar or molasses, the yeast grows, feeding 
on the sugar and very decidedly chang- 
ing in its nature. Bubbles of gas rise 
through the liquid in which the yeast 
is growing (Fig. 7). Besides this gas 
there is produced at the same time a 
certain amount of alcohol which re- 
mains in the liquid. When the sirup 
has become entirely fermented, the 
sugar has disappeared and alcohol has 
taken its place. 

It is not always necessary to add 
yeast in order to start fermentation. 
Grape juice is changed into wine and 
apple juice into cider without any 
yeast being put into them. But in 
these cases a ferment gets into the 
juice from the air. These air ferments 
are in reality almost the same thing 
as the yeast from the store. Like 
yeast they are tiny plants, so small and 
light that they are blown about in the 
air and are always ready to act upon 
sugary liquids if thej^ fall into them. 
Fermented and Distilled Liquors. — Alcohol is found 
in many kinds of drinks. Such drinks are usually 
called Hquors. They are always made by the fermenta- 
tion of some such substance as sugar^ molasses^ malt^ 



Sugar 
Solution 



-Carbonic 
Dioxide- 
Gas 



Alcohol 
'left in 
Solution 



s?^^^^— Yeast 

Fig. 7. — Sugar 
solution undergo- 
ing fermentation 
by yeast. 



FOODS AND FOOD MATERIALS 



29 



corn^ grape juice^ or apple juice. These materials are 
fermented by yeast which is sometimes added directly 
to them, and sometimes gets into them from the air. 
In the latter case the fermentation is not so rapid as 
in the former. All the liquids contain alcohol as soon 
as they begin to ferment, whether they have been 
mixed with common yeast or whether they simply con- 
tain ferments from the air. 

The mixtures thus fermented are employed in various 
ways. They may be used for drinks just as they are. 
This is the case with heer^ ale^ wine^ and cider. Such 
drinks are called fermented liquors. The amount of 
alcohol which they contain ranges from one fiftieth to 
one fifth of the total volume of the liquor. The rest of 
the material is principally water, the amount of solid 
matter dissolved in the mixtures being small (Fig. 8). 




Fig. 8. — Showing the proportion of alcohol and water in 
beer, wine, and whisky. 



Certain drinks called distilled liquors are made 
from fermented mixtures. By the process known as 
distilling, a part of the water is taken away, thus 



30 PHYSIOLOGY AND HYGIENE 

leaving a larger proportion of alcohol in the mixture. 
The strength of the liquor depends, of course, upon 
the amount of alcohol which remains. The propor- 
tion of alcohol in the distilled liquors used as drinks 
varies from one quarter to one half. The rest of the 
material, which is chiefly water with a little flavor- 
ing matter, contains nothing useful except the water 
itself. The distilled liquors include rum^ whisky^ 
gin, and hrandy. Because of their large proportion 
of alcohol, such drinks are even more harmful than 
fermented liquors. A small amount of whisky will 
intoxicate much more quickly than a large amount 
of beer or ale. 

There is nothing in either fermented or distilled 
liquors that makes tliem necessary to any person in 
sound health. The boy or girl who wishes to be as 
vigorous, as useful, and as successful as possible should 
let them alone. 

Why People drink Alcohol. — Although when taken 
in small quantities alcohol acts as a fuel, the danger 
that attends its use is so great that it is unwise to 
use it for food purposes. Men do not drink alcohol 
because it gives heat and power. A few cents' Avorth 
of bread will supply more heat and muscular strength 
than can be obtained from a much larger sum of money 
spent for any form of alcoholic drink. The alcoholic 
drinks may perhaps quench thirst, but it is only be- 
cause of the water they contain, and Avater would serve 
the purpose much better if used alone. 

Why, then, are alcoholic drinks used? In the first 



FOODS AND FOOD MATERIALS 31 

place some persons enjoy the taste, although pure alcohol 
is unpleasant to the taste, and most beers and wines 
are disagreeable at first to the majority of people. Then 
there are those who enjoy the excitement which the 
alcohol produces, and there are others who have become 
so accustomed to using alcoholic drinks that they find 
it difficult to overcome the habit. It is here that the 
greatest danger in using alcoholic liquors lies. They 
are apt to create an appetite for more and more alcohol. 
Some people do not fall victims to this appetite ; others, 
who seem to be just as strong and as capable of resist- 
ing the appetite, are finally mastered by it. No one is 
so safe from this danger as he who never begins to use 
alcoholic drinks. 

People do not drink alcohol because they consider it 
valuable as a food, but because they like the taste or 
^the exhilaration it produces, or because they cannot 
overcome the appetite for it. 

AMOUNT OF FOOD NEEDED 

How much food we should eat is a question not 
easy to answer. The amount depends somewhat upon 
a person's occupation. If a locomotive is running fast, 
it needs more fuel than if it moves more slowly, and 
when it stops, it requires only sufficient coal to keep 
the fire burning. So long as we live, our bodies never 
entirely cease action, for the heart always continues 
to beat ; but at certain times we are more active than 
at others, and when we are hard at work, more food 
is required than when we rest. A poorly fed person 



32 PHYSIOLOGY AND HYGIEXE 

cannot do hard work. If a man, from a false idea of 
economy, subsists largely upon starchy foods, like pota- 
toes and rice, he will be unable to do as much hard 
work as his neighbor whose diet contains more of the 
muscle-building materials. The man of small income 
should spend more of his money on beans or cheese, 
or perhaps on skimmed milk, as these will aid in sup- 
plying strength for muscular work. 

The using of the body substance for muscular 
strength can be tested with the aid of scales. If a boy 
be weighed carefully before taking active exercise for 
an hour or two, and again after the exercise, the scales 
will show a difference in his weight. If the weighing 
is accurate and the boy has taken neither food nor water 
between the two weighings, the scales show just how 
much of the body substance has been used up during 
the muscular action, and consequently how much food 
and water are required to replace the loss. 

Cheap and Costly Foods. — The cheapest food is not 
necessarily the one that costs the least money, but the 
one that gives us the greatest food value in return for 
a given outlay. In this sense the cheapest foods are 
beans and peas, since they cost little and yet give us a 
large amount of body-building material. Meats, on the 
other hand, although nutritious, are more expensive. 



FOODS AND FOOD MATERIALS 



33 



COMPARATIVE FOOD VALUES 

The following table shows the food values which can 
be obtained for ten cents : — 

COMPAKATIYE COST OF DIFFERENT FOOD MATERIALS 
AT AVERAGE PRICES. 



Kind of Food Material 



Price 

per 

pound 



Cost of 
1 pound 

pro- 
teids 1 



Amounts for ten cents 



Total 
weig-ht 
of food 
material 



Proteid 



Fat 



Starch 



Beef, sirloin . . . 
Beef, round . . . 
Mutton .... 

Pork 

Pork-fat, salt . . 

Butter 

Eggs, 24^ a doz. 

Cheese 

Milk, 6^ a qt. . . 
Wheat flour . . . 
Corn meal, granular 
Wheat breakfast food 
Oatmeal .... 

Rice 

Wheat bread . . . 
Beans, white dried 
Corn, canned . . 
Potatoes, 00 f a bush. 



Cents 

25 
16 
16 

18 
12 
25 
16 
16 

3 

3 

4 



10 
1 



Dollars 

1.60 
.87 

1.10 

1.30 

6.67 
25.00 

1.39 
.64 
.94 
.31 
.32 
.73 
.29 

1.18 
.64 
.29 

4.21 
.67 



Pounds 

0.40 

.63 

.63 

.56 

.83 

.40 

.63 

.63 

3.33 

3.33 

4.00 

1.33 

2.50 

1.25 

2.00 

2.00 

1.00 

10.00 



Pounds 

0.06 
.11 
.09 
.08 
.02 

.07 
.16 
.11 
.32 
.31 
.13 
.34 
.08 
.16 
.35 
.02 
.15 



Pounds 

0.06 
.08 
.09 
.18 
.68 
.32 
.06 
.20 
.13 
.03 
.07 
.02 
.16 

.02 
.03 
.01 
.01 



Pounds 



.02 

.17 

2.45 

2.96 
.98 

1.66 
.97 

1.04 

1.16 
.18 

1.40 



1 The cost of one pound of proteids means the cost of enough of the 
given material to furnish one pound of proteids, without regard to the 
amounts of other food substances present. 



34 



PHYSIOLOGY AND HYGIENE 




Proteids 



This table shows the comparative amount of the dif- 
ferent food materials which can be purchased for ten 
cents. It shows that beans give the most proteid for 
the money and oysters the least. 



FOODS AND FOOD MATEFvIALS 




Proteids Fats 5"f«^ 5«r^«; Water Refuse 
Mattel's hydrates 



This table shows the amount of the different food 
materials contained in the different foods. From this 
it will be seen that cheese is the most nutritious food. 
Beef is also very nutritious, but its high price makes it 
an expensive food, as is shown by the table on page 34. 



36 PHYSIOLOGY AND HYGIEXE 

QUESTIONS 

1. For what purposes do we need food ? 

2. AVhat are the two classes of foods? 

3. In what respect is meat a valuable food ? 

4. Why are beans especially useful as foods? 

5. If we drink skimmed milk, what food will go well with it ? 

6. Of what use to the body are starch, sugars, and fats? 

7. With what does albumen furnish the body ? 

8. Why is milk made more healthful by boiling? 

9. Why do people buy porterhouse instead of round steak ? 

10. What food substances do we get from cereals? 

11. Why are potatoes so widely used as foods? 

12. Which would be the best meal : one made up of potatoes 
and rice, or one of potatoes and beans ? 

13. Why are not potatoes alone a good diet? What kind of 
food should we eat with them ? 

14. What is the chief use of fruits and vegetables ? 

15. Why do we need to drink water? 

16. How can impure water be made fit for drinking? 

17. What does alcohol look like ? How is it made? 

18. Why do people use alcoholic drinks? 

19. What food do w^e get from cheese ? What does this food do 
for the body ? 

20. If you had one dollar to spend for a meal for four persons, 
what would you buy to make the most useful meal? (Consult 
tables on pp. 33-35.) 



CHAPTER II 
DIGESTION 

Befoee the bread and butter which we eat for 
breakfast becomes the blood and later the muscle of 
our body it meets with a number of changes. The 
process by which the food taken into the body is 
changed so that it can be absorbed into the blood, and 
thus be used for growth, repair, and warmth, is called 
digestion. Certain organs of our body have charge of 
this work and are called the digestive organs. 

THE MOUTH 

The food is received into the mouth, where the 
first step is taken in preparing it to enter the blood. 
The mouth is a large cavity with the cheeks for its 
sides, the tongue for a floor, and the palate for a roof. 
The front part of the palate is a hard, flat bone. The 
back part is a soft membrane, with a little finger-like 
piece called the uvula hanging from the middle and 
reaching almost to the tongue. (See Fig. 10.) 

The Teeth. — Around the sides and front of the 
mouth are two rows of teeth fastened securely in 
sockets in the jawbones. The front teeth have sharp 
edges for cutting or biting food, while those farther back 

37 



38 PHYSIOLOGY AND HYGIENE 

in the mouth have broader surfaces and are used for 
grinding or chewing the food into a fine mass. Each 
tooth consists of a crown, the part we see as we look 
into the mouth; a neck, which is surrounded by the 
gums; and a root, which fits into the socket in the jaw- 
bone. Each tooth has a tiny blood vessel entering 
through its root, and is also supplied with a nerve. 
When the nerve is exposed to the air as a result of 
decay, the tooth may ache. The crown of the tooth is 
covered with enamel, the hardest substance in the body. 

Growth of the Teeth. — In the course of life we have 
two sets of teeth. The first, or milk teeth, begin to 
groAv when the child is five or six months old, and they 
continue to appear, one after another, for about three 
years. The milk teeth are twenty in number. When 
the child is about six years of age, the second, or perma- 
nent teeth, begin to push their way through the gums ; 
the milk teeth are gradually loosened as the others push 
their way out. The first of the permanent teeth, called 
the '' six -year molars," come so early that they are often 
mistaken for the last of the milk teeth. The permanent 
teeth are thirty-two in number. 

Figure 9 shows the permanent teeth. Their arrange- 
ment, as can be readily seen from the figure, is as 
follows, beginning at the middle of the upper set: two 
incisors, one canine, two bicuspids, and three molars. 
The other side of the upper row is similarly arranged, 
and the lower jaw holds sixteen teeth to match these, 
with names corresponding. Notice the sharp edges of 
the front teeth and the broad grinding surfaces of the 



DIGESTION 



39 



double teeth farther back ; also the six-year molars. 
If you shut your teeth tightly together, you will appre- 
ciate how well the upper and lower teeth match. The 

edges of the upper 

Jnchon 
Xoninc 




^^ Molar' 
Z^Molarj 



Fig. 9. — The Upper Teeth. 



front teeth slip 

over those of the 

corresponding 

lower teeth, so 

that the food may 

be bitten off as if 

cut by scissors. 

The projections of 

the upper back 

teeth are opposite 

the hollows of the corresponding lower ones, so that 

the food may be ground fine without difficulty. 

Care of the Teeth. — The teeth, when once they are 
fully grown, will never repair themselves. If a bone 
of the arm is broken, the two edges can be set in the 
proper position, and the bone Avill knit, or groAV to- 
gether again. If, on the other hand, a tooth is broken 
off or worn out, it will never repair itself. Teeth are 
liable to decay. The outside of the tooth, the enamel, 
is hard, but the inside is comparatively soft. As 
long as the enamel is in perfect condition, tlie tootli 
will remain sound, but if there is a crack in the 
enamel, decay is likely to start at the crack and enter 
the soft part inside. The tooth tlien decays rapidly 
until it is ruined. Even a very small hole in the 
enamel may result in a large cavity in the softer sub- 



40 



PHYSIOLOGY AND HYGIENE 



stance within. We should never pick the teeth with 
anything hard, such as needles or pins, because these 
are liable to scratch, and so crack, the enamel. For 
the same reason we should not crack nuts or other 
hard substances with the teeth. It is also harmful to 
the teeth to take extremely hot and cold foods or 
drinks in close succession. 

Particles of food lodged between the teeth become 
decayed and help to decay the teeth in turn. It is 
well, therefore, to brush the teeth after each meal, and 
also at night, so as to remove any bits of food that 
might do injury if allowed to remain. To keep the 
teeth healthy and sound, it is necessary, in addition 

to brushing 
them, to re- 
move, with a 
soft toothpick 
or thread, all 
bits of food 
which cling to 
them. When 
a tooth begins 
to decay, it 
should be at- 
tended to at 
once by a den- 
tist ; for if 

the small cavities are promptly filled, the tooth may 
perhaps be preserved for years, and much pain and 
expense be saved. 



Uvula - 

Pi I Ian or 
Fauccd •. 




Fig. 10, — The Mouth. 
Showing the opening into the throat. 



DIGESTION 



41 



Figure 10 shows the open mouth as it appears when 
we look within. Notice the palate and the uvula. 
By placing the tip of the tongue on the roof of the 
mouth just inside the upper teeth and drawing the 
tongue slowly backward over the roof of the mouth, 
we can discover the difference between the hard and 
soft portions of the palate. 

Salivary Glands. — If some one says the word ''lemon," 
our mouths are apt 
to water, as we think 
how sour the juice 
of the lemon is. The 
fluid which moistens 
the mouth, and 
whose flow is thus 
increased by the aid 
of the imagination, 
comes from the 
organs known as the 
salivary glands. The 
liquid produced is 
called saliva. There 

are three pairs of Tig. 11.— A DiaCxRam of the Side of 

salivary glands. the Face. 

Showing the position of the salivary 
Those who have had giands and their ducts. 

the mumps can locate 

one of these pairs of glands without difticulty. Tliese 

are the parotid glands, which are inflamed and swoUen 

in that painful disease. They are situated just boKnv 

and a little in front of the ears. There are two sali- 




c^j^^~ -Parotid 



dolivaty dland^ 



42 PHYSIOLOGY A^D HYGIENE 

vary glands under tlie lower jaw and two more beneath 
the tongue. All these glands are connected with the 
mouth by little tubes, called ducts, which carry the 
saliva from the glands into the mouth. The saliva 
is poured out of the tubes whenever it is needed. 
Although the salivary glands are constantly sending 
out enough saliva to keep the mouth moist, the act of 
chewing stimulates the action of the glands so that the 
amount is largely increased. 

Figure 11 shows the salivary glands on one side of 
the face, also the ducts that connect them with the 
mouth. 

FOOD IN THE MOUTH AND THROAT 

Need of Mastication. — After we have taken a bite of 
bread and butter, the first step towards its digestion is 
chewing or mastication. We chew our food to break 
it into small pieces so that the saliva may become 
thoroughly mixed with the food, and also that the di- 
gestive juices may afterwards do their work easily. 
The digestive juices in the stomach can act only on the 
outside of each piece of meat, and therefore the smaller 
the pieces, the shorter the time required to digest themo 

Many a person suffers from dyspepsia as a result of 
the foolish habit of swallowing his food partly chewed. 
Rapid eating is injurious, since it forces the stomach 
to do work that belongs to the teeth. Very solid foods, 
like nuts or hard-boiled eggs, can be digested properly 
only after they are thoroughlj^ chewed. Some foods, 
such as oatmeal and mushes of different kinds, do not 



DIGESTION 43 

need much mastication, but solid food should not be 
swallowed until it is ground into a fine pulp. 

Use of Saliva. — While the food is being chewed it 
is moistened by the saliva that is poured into the mouth. 
The saliva serves two different purposes. 

1. Saliva moistens the food and the mouth, — If the 
mouth becomes dry, for any reason, we are very uncom- 
fortable, and even talking is difficult. Sometimes, if we 
are frightened, the glands stop producing saliva entirely, 
and as a result we find it difficult to swallow. How 
impossible it is to swallow food that is not thoroughly 
moist may be comprehended by eating a cracker. 

2. Saliva begins the process of digestion, — The water 
in the saliva dissolves some of the foods, like sugar, 
but this is not digestion proper. If, however, we 
chew a bit of bread for a few minutes, we find that 
it becomes a trifle sweet. The saliva changes the starch 
into sugar. The change begins as soon as the food is 
mixed with the saliva. It is the beginning of real 
digestion, although ordinarily the starch does not remain 
in the mouth long enough for much of it to be thus 
acted upon. If the food is acid (sour), as when it is 
mixed with vinegar, no change takes place in the mouth. 

The amount of saliva in the mouth may be increased 
by chewing gum. In the case of an athlete who wishes 
to keep his mouth moist during exercise, gum chewing 
may be useful. Under ordinary circumstances, how- 
ever, not only is the habit vulgar and impolite to the 
people about us, but the constantly stinudated action 
of the salivary glands is probably injurious. 



44 



PHYSIOLOGY AND HYGIENE 



Tonsils. — At the back of the mouth, as may be seen 
in Figure 10, there is a large opening leading to the 
throat. As soon as the food is chewed and moistened 
it is pushed back by the tongue through this opening. 
At each side of the opening may be seen a small 

rounded body 
called a tonsil. 
Sometimes 
when a per- 
son has taken 
cold, the ton- 
sils become 
swollen, and a 
kind of sore 
throat called 
tonsilitis re- 
sults. It is 
not known 
whether the 
tonsils have 
a special use 
or not. 

The Throat. 
— A cavity, 
called the 
throat, is situ- 
ated just back of the mouth. Into this the food passes 
after being chewed. The upper part of the throat 
opens into the nasal cavity, and from there, by way of 
the nostrils, to the exterior. Thus both the mouth 




Fig. 12. — A Section through the Head. 
Showing the relation of mouth, throat, etc. 



DIGESTION 45 

and the nostrils are connected directly with the throat. 
Figure 12 shows this relation. 

Two large tubes open downward from the throat. 
One, the gullet or oesophagus, extends to the stomach ; 
the other, the windpipe or trachea, connects with the 
lungs. The windpipe is placed in front of the oesopha- 
gus, and it opens at the top, so that the air we 
breathe may pass into it readily. The opening is the 
glottis. If a particle of food drops into the windpipe, 
it causes violent coughing and sometimes choking. 
To keep food from entering the windpipe as it passes 
over the entrance on the way to the gullet, the wind- 
pipe is provided with an elastic lid, somewhat like soft 
India rubber, which rests upon the opening. 

When we are breathing, this lid, which is called the 
epiglottis, is lifted as in the illustration (Fig. 12); but 
as food passes from the mouth, the lid closes for the 
moment so as completely to cover the opening into the 
windpipe and allow the food to slip safely over. As 
soon as the food has passed, the lid flies up again, and 
the windpipe is open once more, read}^ for its regular 
work of carrying air to the lungs. 

If we talk or laugh while our mouths are full of food, 
or while we are drinking, a bit of the food or water is 
liable to ''go down the wrong way" ; that is, we may 
have the epiglottis open for a breath just at tlie moment 
the food or water ought to pass over to the cvsophagus. 
Some of it then drops into the windpipe instead of slip- 
ping over the top, and violent coughing results, until 
the foreign matter is coughed out. 



46 PHYSIOLOGY AND HYGIENE 

Figure 12 shows a section of the head, indicating the 
shape of the throat and the openings into the mouth and 
nose, with the location of the windpipe and oesophagus. 
Notice the epiglottis at the top of the windpipe. 

Sore Throat. — Any soreness of the tonsils, the palate, 
or the throat makes swallowing painful, and we say we 
have a sore throat. Sore throat, especially in the case 
of children, should receive immediate attention. If a 
child feels any soreness when swallowing, his throat 
should be examined, and if there are whitish spots on 
the palate or the tonsils, a physician should be called 
at once, as the trouble may be serious. 

Swallowing. — After the food reaches the throat it is 
rapidly swallowed. While food remains in the mouth 
we can control it, but the moment it enters the oesopha- 
gus it has passed beyond our control. If we should 
then discover that it was poison, we should be obliged to 
keep on swallowing just the same. The food is pushed 
through the oesophagus into the stomach by the muscles 
of the throat and oesophagus. It does not simply fall, 
but it is actually forced down. A person can swallow 
water even when he is standing on his head, and a horse, 
when he drinks, of course swallows the water upward. 

FOOD m THE STOMACH 

The Stomach. — A few seconds after the food has 
entered the oesophagus it passes into a large cavity called 
the stomach (see Figs. 13 and 15). This is a chamber 
similar to a gourd in shape, lying just below the ribs 
and a little to the left side of the body. It is closed at 



DIGESTION 



47 



Liver 



Valve 



Oesophagus 



■Pancreas 
.Jp/een 



both ends by small folds or valves. The valve between 
the oesophagus and the stomach ordinarily prevents the 
food from going back into the oesophagus. Sometimes, 
however, when ill- 
ness causes us to 
vomit or '' throw 
up," the valve be- 
tween the stomach 
and the (jesophagus 
opens and allows 
the food to return 
to the mouth. The 
valve at the lower 
end, which con- 
nects with the tube 
called the intestine, 
prevents the food 
from leaving the 
stomach too soon. 
Figure 13 shows 
the stomach with 
its valves. The 
stomach itself is 
elastic, and will 
stretch so as to 
hold a large amount 
of food, but it 
shrinks again as soon as the food passes out. The 
stomach of an ordinary grown-up person can hold three 
pints of food very comfortably. 




^■Vent 

Fig. 13. — The Digestive Orgaxs of 
THE Abdomen. 



48 



PHYSIOLOGY AND HYGIENE 



The outer walls of the stomach consist principally of 
muscular fibers which run around it in various directions, 
some crosswise, some lengthwise, and some obliquely. 
As these fibers contract and relax, they cause the 
stomach to undergo a variety of motions, which mix 
together the different foods inside and keep them 
moving around and around. As long as the food 
remains in the stomach it is thus kept in constant 
motion. 

The inner lining of the stomach contains hundreds 

Inner Surface of Stomach 




Fig. 14.- 



Oostric 
Glands 



Mu5cles 



Mu5des 



-A Section of the Wall of the Stomach. 

Highly magnified. 



of thousands of tiny glands. Each of these glands 
is shaped somewhat like a little bottle, with its mouth 
opening into the stomach, as shown in Figure 14. The 



DIGESTION 49 

glands produce a liquid called gastric juice, which is 
poured out of their mouths into the stomach. 

Action of the Gastric Juice. — As soon as the food 
enters the stomach, the glands begin to pour gastric 
juice upon it. At the same time the stomach, by con- 
tracting, begins to churn the food, and mix it with 
the gastric juice. In a short time the two are com- 
pletely mixed, so that the gastric juice can begin to 
act upon the food and produce in it the changes that 
we call digestion. 

Action on Starch, — When we chewed our mouthful 
of bread until it turned sweet, we found that the 
saliva had changed some of the starch in the bread 
to sugar. This digestive action of the saliva upon the 
starch is stopped as soon as the gastric juice begins to 
work upon the food. This is because the gastric juice 
is an acid,, and we have already learned that the presence 
of anything sour prevents the action of the saliva upon 
starch. The starch, then, is not digested in the 
stomach, but it will be taken care of farther on. 

Action on Meats, — A portion of the work of the gas- 
tric juice is to break the food into small parts. j\Ieat 
is made up of a great number of tiny threads, called 
muscle fibers, which are glued together b}^ a material 
that holds them in little bundles. The gastric juice 
dissolves this gluey material, and the fibers fall apart. 
Just as soon as the juice gets them separated it pro- 
ceeds to act upon each one separatelj^, changing it 
to a liquid form ready for the blood to take up, or, 
as we say, digesting it. We have noticed (see Fig. 'S) 



50 



PHYSIOLOGY AND HYGIENE 



OesophdgiiS 



LStomdc/i 
'-Large Intestine 
'SmJIJntestine 



that the fat is in little sacs held together by a connect- 
ing mass of threads. Both the sacs and the threads 
are dissolved by the gastric juice, so that the fat floats 
about freely in the stomach. 

Action 071 Proteids, — It is also a portion of the work 

of the gastric juice to 
get the proteids ready 
for the blood to use as 
the building material of 
the body. We found, 
when we cooked the 
albumen of the egg and 
when we caught the glu- 
ten of flour in muslin 
cloth, that these proteids 
could not be dissolved in 
water. But, until these 
substances are in liquid 
form, they cannot be 
taken up by the blood. 
What the gastric juice 
does for the proteids is 
to change them in such a 
way as to make it possible 
for them to dissolve in 
the water that is in the stomach. After the gastric juice 
has done its work, a part of these glutens, albumens, and 
caseins become dissolved and are ready to enter the blood. 
Usually a part of the proteid food leaves the stomach 
undissolved and is changed to a liquid form later. 




Fig. 15. — Showing the Location 
OF THE Digestive Organs. 



DIGESTION 51 

Actloii on Milk, — After a hearty meal a baby often 
throws up a part of his milk in a curdled condition. 
This does not mean that the stomach is ''sour," but 
simply that the child has overfilled his stomach. The 
milk ought to be curdled in the stomach, and if it 
did not curdle, it would mean that the stomach was 
out of order. The curdling has been caused by the 
gastric juice. The gastric juice in a baby's stomach 
curdles the milk more readily than that in the stomach 
of a grown person, but under all circumstances curdling 
is the first step in the healthful digestion of the milk. 
The curdled milk looks exactly as if it had soured. 

We can see just how the curdling takes place by put- 
ting a teaspoonful of rennet or a rennet tablet (to be 
had at the druggist's) into a cup of milk warmed to 
about the temperature of the body (98°). In the 
course of half an hour the milk will be curdled. Notice 
that the curd, which is casein, is a solid mass. In the 
stomach this curd is later dissolved again. 

Chyme. — We swallow our food in the form of solid 
meat, solid bread, and liquid milk, and in a short time, 
from an hour and a half to three hours, it becomes 
quite changed. It is now a tliick liquid. The fats, 
freed from their sacs, as we have seen, have been melted 
by the heat of the body; the meat has been divided 
into threads and partly dissolved; the sugars have been 
dissolved in the water; some of the starches have been 
turned to sugar and also dissolved; while the milk has 
been curdled and partly turned to liquid form again. 
These materials have been churned bv the motions of 



52 PHYSIOLOGY AND HYGIENE 

the stomach until they are thoroughly mixed together. 
They now form a gray, slimy mass called chyme. 

Although we pay no attention to the matter and 
think little about it, our hearts continue their accus- 
tomed beating, hour after hour and day after day. 
And so it is with the stomach's work. We do nothing 
to supply the materials required by the body except to 
eat w^hen we are hungry, and yet the wonderful work 
of digestion goes on, usually without inconvenience 
to us. 

A Few Good Rules. — Though we cannot do much to 
help the stomach in the churning and digesting process, 
we may assist it by our manner of eating our food. 
If we are too thoughtless of the rights of the stomach, 
we are certain to receive our just punishment sooner 
or later in the form of indigestion and dyspepsia. 

We can aid the stomach and preserve our own health 
by following a few simple rules. 

We should eat slowly and be sure that the food is 
well chewed before it is swallowed. The habit of eat- 
ing often between meals is very trying to the stomach, 
since it keeps the gastric glands in constant action. We 
should never eat a hearty meal when we are either very 
tired or very warm; it is wise to rest first. No hard 
work, either mental or physical, should be entered upon 
for at least half an hour after a hearty meal. This is 
the stomach's busiest time ; we should help it as much 
as possible by keeping the rest of the body quiet. 

We should be careful as to the quantity of water that 
we drink with our meals. Some water is required, but 



DIGESTIO:Nr 53 

the food should never be ''washed down" with water. 

Nor is it well to drink much water immediately before 

a meal. Ice-water, if drunk at all, should be sipped 

slowly, so that as it passes down through the throat, it 

may be warmed more nearly to the temperature of the 

stomach. 

FOOD IN THE INTESTINES 

After the food has spent from one to two hours turn- 
ing around and around in the stomach, the fold forming 
the valve or lid to the intestine opens and allows a small 
amount to pass out. The contents of the stomach thus 
from time to time pass into the intestines, until, at the 
end of three or four hours, the outlet relaxes and allows 
the remaining food to leave the stomach, even though 
some of the particles may still be quite solid. The 
stomach is now empty, and, after a rest, is ready for the 
next meal. 

The Intestines. — The food which has passed through 
the opening at the lower and smaller end of the stomach 
enters the intestines, more commonly called the bowels. 
The intestines consist of a long tube, very much coiled, 
filling the larger part of the abdomen below the stom- 
ach, as is shown by Figures 13 and 15. The part which 
is connected witli the stomach, or the small intestine, is 
from one to two inches in diameter, and about twenty 
feet long. The large intestine is about two and one 
half inches in diameter and five feet long. 

The Liver. — We all have seen the liver of the ox or 
calf either exposed for sale at the market or on the 
breakfast table cooked with bacon. The human liver 



54 PHYSIOLOGY AND HYGIENE 

resembles the ox liver very closely. It is of a dark 
reel color, and lies a little above and at the right of 
the stomach. It is one of the largest organs in the 
body, weighing several pounds, and it is one of the 
most important. It produces a liquid called bile. The 
bile passes through a tube and empties into the intes- 
tines near the stomach. When digestion is not going 
on, the bile collects in a little sac at the lower side 
of the liver, known as the gall bladder^ Figure 13 
shows the liver, the gall bladder, and its tube or duct. 

The Pancreas. — The pancreases a long, somewhat 
thin gland, placed just below the stomach. Tliis also 
produces a liquid secretion which passes through a tube 
and empties into the intestines. This liquid, which is 
called the pancreatic fluid, empties into the intestines 
with the bile. Thus the food from the stomach is 
mixed with the bile from the liver and the fluid from 
the pancreas almost as soon as it enters the intes- 
tines. Notice the pancreas, with its duct, as shown in 
Figure 13. 

Use of the Liver. — Probably most of us know from 
experience how a person looks and feels Avhen he is 
''bilious." The skin becomes a dull yellow, the eyes 
lose their sparkle, and the person seems to lose all 
his ambition without being sufficiently ill to be con- 
fined to his bed. Tire trouble is that the bile has 
ceased to pass freely from the liver. Tlie bile aids the 
pancreatic fluid in its work of digestion, especially on 
fats, tends to prevent decomposition in the contents of 
the intestines, and aids in the regularity of tlie action 



DIGESTION 55 

of the bowels. But the bile is, however, chiefly a waste 
product^ and it pours into the intestines partly as a way 
of disposing of itself. The liver has several duties to 
perform, but one important duty is to help to remove 
this waste material. When, for any reason, the bile 
cannot thus escape into the intestines, it passes back 
into the blood in the liver, and is then carried to all 
parts of the body, producing illness and turning the 
skin to a peculiar yellow. We then say we are bilious. 

Changes in the Intestines.- — As soon as the food enters 
the intestines it is mixed with the secretions from the 
liver and pancreas. Further changes are at once pro- 
duced in the food, principally by the pancreatic fluid. 
The pancreatic juice acts upon all kinds of food in such 
a way as to make liquid those not already dissolved. 

Starch. — We have learned that most of the starch 
escapes from the mouth without being turned into 
sugar by the saliva and passes into the stomach and 
out again to the intestines, still in the form of starch. 
But the pancreatic juice has just the same effect on 
starch as has saliva — it turns the starch to sugar. 
The pancreatic juice takes up and completes this work 
of -changing starch into sugar. The sugar is then dis- 
solved like all of the other food. 

Proteids. — The pancreatic juice has the same effect 
upon the proteids as the gastric juice. It changes into a 
soluble form any proteids that may have passed into the 
intestines in solid state, whether they be the lean part 
of meat, the gluten of the wheat, or the casein of milk. 
The food in the intestines becomes more and more lii][uid. 



56 PHYSIOLOGY AND HYGIENE 

Fats. — The last we knew of the fats they formed an 
oily mixture in the stomach, where the gastric juices 
could not act U230n them. When they pass into the 
intestines the pancreatic juice begins to digest them. 
We have already seen that when we shake olive oil 
with water, the water separates the oil into minute 
drops that float, making the liquid look milky. In a 
somewhat similar way the pancreatic juice acts upon 
the fats as they pass along the intestines. It breaks 
the fat into millions of tiny drops which are mixed with 
the contents of the intestines, giving the whole mass a 
milky white appearance. The breaking up of the fat 
into drops is the digestion of fat. The fat is not actu- 
ally dissolved like the sugar, but when it is broken up 
in this way the particles of fat are small enough to 
pass into the blood. 

Chyle. — The food was swallowed as solid bread, 
meat, and potatoes, but now, after from two to four 
hours or more, it has become in the intestines a milk- 
white liquid, somewhat thicker than milk, but not so 
thick as molasses. It is called chyle, and it contains 
most of the foods, dissolved into liquid form. The 
food is now ready to be absorbed into the blood vessels. 

THE DIGESTIBILITY OF FOODS 

If our food were not digested, it would be of no more 
use to us than stones, for it could not be taken into the 
blood. People who have weak digestive organs suffer 
from lack of food, no matter how much they eat. For 
this reason the value of the food we eat depends as 



DIGESTION 



57 



much upon whether it is easily digested as upon the 
food substances that it contains. 

Cheese, for example, contains a very large amount 
of valuable food, but it is so hard to digest that it is 
less useful than meat, which, although it contains less 
food than cheese, digests more easily. Beans are in 
some respects a more nourishing food than meat, but as 
they do not digest so easily, much of their value may 
be lost, passing away in the waste. 

In choosing what we shall eat we should be careful 
not to load the stomach with food hard to digest. 
Although it is perfectly safe, if we are strong and well, 
to eat some foods that do not digest easily, we should 
not do so frequently. The following table will give us 
a little idea of some of the more easily digested foods 
and some of those less easily digested : — 



Foods Easy to Digest 


Foods Difficult to Digest 


Milk' 


Fried foods 


Bread 


Beans and peas 


Rice 


Hard-boiled eggs 


Raw oysters 


Pork 


Soft-boiled eggs 


Veal 


Boiled beef 


Cheese 


Mutton 




Boiled chicken 




Broiled meats 





Boiled or broiled foods are, in general, more quickly 
digested than those that are roasted, because boiling 



58 



PHYSIOLOGY AND HYGIENE 



softens the solid foods so that the digestive fluids can 
act upon them. Fried foods are more difficult to digest 
than the same foods cooked in any other way, since 
the frying is apt to soak the food with fat, which makes 
it difficult for the digestive juices to act. 



5/ood {/e5S€/3 



^.Lacttoh or 



HOW THE FOOD GETS INTO THE BLOOD 

All this process has not yet put the food where it 
can be used to build up, repair, warm, and provide 
muscular power for the body. We are now ready for 
the final chapter of our story — how the digested food 
gets into the blood. 

We have learned that by the time the food has been 

in the intestines 
from two to four 
hours it has all 
become digested 
and turned into 
chyle. The long in- 
testinal tube which 
holds the chyle, is 
not loose in the 
body, bat is held 
in position by a thin 
sheet. Such a sheet 
is called a mem- 
hrane^ and this par- 
ticular one is the mesentery. It is folded many times 
and is wrapped around the intestines as shown in Figure 
16. There are many hlood vessels in the mesentery. 




/ntest/ne-i 



EiG. 16. — A Bit of the Intestine. 

Showing how it is held in position by the 
mesentery. 



DIGESTION 59 

some of them carrying blood to the intestines, and 
others carrying the same blood away again. These 
blood vessels take away a large part of the digested food. 
A bit of the intestinal wall is shown in Figure 17. 
The wall is rather thick and has two layers of muscles. 



Villi 




Glands 



^"^^^^Mu^cl^ 



EiG. 17. — A Bit of the Intestine. 
Showing the muscles, glands, and the numerous villi on its 
- under surface. Moderately magnified. 

The inside surface is covered with tiny projections, 
like little fingers, extending inward. They are called 
villi. Figure 17 shows some of the villi enlarged, so 
that we may see what they are like. Villi are really 
so very tiny that they can only just be seen with the 
naked eye. There are millions of them, so many that 
they line the whole inside of tlie intestines, giving it a 
soft, velvety surface. 

Duties of the Villi. — The villi are very interesting to 
stud}^, for they take the digested food out of the intes- 
tines and give it to the blood. Unlike the glands of 



60 



PHYSIOLOGY AND HYGIENE 



Epithelium 



3loo(/ 
l/essel 



the stomach, of which we have learned, these villi have 
no opening -into the intestines. Their walls, however, 
are so thin and so delicate that the dissolved food can 
pass through them readily. A single one of these little 

bodies, much magnified, is 
shown in Figure 18. It is 
covered on the outside with 
tiny cells, which form the 
epithelium. Inside there 
are a great many minute 
blood vessels. One blood 
vessel, the artery, brings 
blood into the villus, and 
anotlier, the vein, takes it 
away. The artery brings 
the blood from the heart; 
tlie vein carries it away to 
tlie liver. 

Just how the villi take 
the food and send it where 
it belongs is a particularly 
interesting chapter in our 
story of digestion. The 
white chyle moving along 
the intestines bathes the 
villi as it passes. Each little 
villus is constantly at work 
taking the digested food from the chyle as it comes 
along, leaving the undigested and waste matters. The 
dissolved sugars and albumens pass through the thin 




A Cell 



Vein 



. ^ -Artery 

lymph Vessel 

or Lacteal 



Fig, 18. — A Single Villus. 
Highly magnified. 



DIGESTION 



61 



membrane into the inside of the villus. Even the par- 
ticles of fat are seized and passed into the inside. Thus 
as the food passes on through the intestines, more and 
more of it is taken up by villi, until most of the useful 
part has been removed. The way in which this food is 
taken into the intestines is illustrated in Figure 19. A 
bladder is tied tightly 
upon a tube and filled 
with water, and the 
whole is then lowered 
into a dish containing 
some sugar dissolved in 
water. It will be found 
after a little time that 
the water inside of the 
bladder has become 
sweet. The sugar has 
passed from the dish 
into the bladder. In 
much the same way the 
sugars and other foods 
pass from the intestines 
into the villi. 

After the food gets into the villi it does not all go in 
the same direction. The sugai^s^ proteids^ icater, and 
salt are taken out of the villi by their tiny blood vessels 
and are carried away in the blood to the liver. Of 
course the starch has already been turned to sugar by 
the digestive processes, so that all the foods go to the 
liver, except the fat. 




Fig. 19. — A simple device for show- 
ing how foods may pass through 
membranes, as they do when they 
enter the villus. 



62 PHYSIOLOGY AND HYGIENE 

The fat takes a different direction. It does not enter 
the blood vessels of the villi at all. The middle of the 
villus, as shown in Figure 18, is a clear space called a 
lymph vessel or lacteal. This opening or tube is made 
to receive the fat, and the little drops of fat pass 
directly into it. The vessels are called lacteals, which 
means milk holders, because the liquid fat with which 
they are filled is white like milk. After taking the fat 
from the intestines the lymph vessels empty it into 
larger, similar vessels and these empty into still larger 
ones which pass through the sheet of membrane sur- 
rounding the intestines. The large lacteals pass up 
through the chest, back of the heart, and empty the fat 
into one of the large blood vessels in the neck, so that all 
of the absorbed food material finally reaches the blood. 

There are thus in the membrane shown in Figure 16 
three sets of tubes : 1. Blood vessels bringing blood to 
the intestines. 2. Other blood vessels carrying the blood 
which has taken up food, from the ijitestines to the liver. 
3. Lacteals carrying fat to the blood vessels in the neck. 

UNDIGESTED PORTIONS OF THE FOOD 

We have learned that the food passes from the 
stomach through the intestines. The material is kept 
moving by a contraction of the wall of the intestines. 
This contraction causes a gentle writhing motion of 
the intestines, which forces the food slowly along. 
The movement is somewhat similar to the w^riggling 
of an earthworm as it tries to make its way along 
the surface of the ground. As the food mass passes on, 



DIGESTION 63 

the villi take up more and more of what can serve the 
body as real food, together with much of the water. 
Finally, very little is left in the intestines except undi- 
gested refuse, together with excretions, like bile, which 
are of no further use. Tliese are waste materials. As 
more and more of the water and dissolved food are 
absorbed, the waste materials become quite solid, until 
they pass out of the body at the vent. The bowels 
should get rid of the waste material every day. Regu- 
lar habits in this respect are necessary for avoidance 
of discomfort and of sickness. 

Now the story of food digestion is nearly completed. 
Let us recall briefly the history of our piece of bread 
and butter. It was carried to the mouth, and was 
bitten off and chewed by the teeth. With the aid of 
the saliva it was moistened and then swallowed. After 
a safe passage over the windpipe, the oesophagus carried 
it to the stomach. There it was thoroughly churned 
and mixed with gastric juice. Little by little it passed 
from the stomach into the intestines, was mingled with 
the bile and pancreatic juice, and then the digested part 
was taken up by the villi, leaving the waste materials 
to be discarded. As we shall see later, tlie food material 
finally reaches through the blood all the parts of the 
body which need it for growtli or work. 



/ 



64 PHYSIOLOGY AND HYGIEXE 

QUESTIONS 

1. What is meant by digestion ? 

2. Why is it necessary to digest food ? 

3. What are the parts of the mouth ? 

4. Of what parts does a tooth consist ? 

5. How many permanent teeth are there ? What are their 
names? 

6. What causes a tooth to decay? 

7. AYhatand where are the salivary glands? 

8. What are the uses of saliva ? 

9. What prevents food from passing into the windpipe instead 
of the oesophagus ? 

10. How does the stomach digest the food? 

11. What is the action of the gastric juices on meats ? On 
proteids ? On milk ? 

12. What is chyme? 

13. What are the liver and the pancreas? 

14. Of what use is the liver ? 

15. What changes are made in starch, proteids, and fats in the 
intestines? 

16. What is chyle? 

17. How does the food get into the blood? 

18. If you chew finely a piece of meat, does saliva start its 
digestion ? How would it be with bread ? 

19. Notice your method of swallowing, and see if you use your 
tongue. 

20. What part of a lunch of bread and butter is digested in the 
mouth ? What in the stomach ? What in the intestines ? 

21. Since cheese is made of milk, why is it not a good food for 
babies ? 



CHAPTER III 

FOOD HABITS AND COOKING 

Unwise habits with regard to eating and drinking 
are probably tlie cause of more sickness than anything 
else. Indigestion, which is very common, may fre- 
quently be remedied more easily by changing the habits 
of eating and drinking than by taking medicine. 

PROPER HABITS OF EATING 

Suppose a company of boys from different parts of 
the world should come together for a picnic. Their 
lunch baskets would contain a good variety of what the 
owners would consider delicacies. The American boy 
would probably have sandwiches and cake; the German, 
rye bread and sausages; the Chinese, some form of rice; 
the young Eskimo, a fish or a piece of seal. Each boy 
would be well nourished and satisfied, if only he had 
enough of his own kind of food. In other words, just 
what we eat is largely a matter of custom and climate. 

We are mistaken if we think we must have certain 
kinds of food, for we can adapt ourselves to almost 
anything, provided it is nutritious and digestible. 
We have a very large variety of foods from which 
to choose, but it is wise to adapt the appetite to 

65 



66 PHYSIOLOGY AND HYGIENE 

what is conveniently obtained. We should particularly 
guard against allowing ourselves to be controlled wholly 
by taste, and we should not refuse to eat what is whole- 
some just because we fancy it is not quite to our liking. 
Substances Avith very strong taste, like mustard, for in- 
stance, we may properly refuse whenever they are dis- 
tasteful, but there is no sensible reason for objecting to 
a dish of oatmeal; Ave can eat it, and learn to like it, if 
we will. 

Cost. — People with small incomes are likely to live 
principally upon starchy foods, such as bread, rice, or 
potatoes, because these are comparatively cheap. But 
we cannot live upon starch and sugar alone. We must 
all of us have some proteids. If we will remember that 
we can get our proteids cheapest in beans and cheese, 
we shall be able to make better use of our money than 
by spending it all for starchy foods. A simple meal of 
bread, butter, milk, cheese or meat, and some vege- 
tables, with perhaps a dessert of fruit or a simple pud- 
ding, is far better than a heavy dinner, with numerous 
courses. Some people make the mistake of having 
too many kinds of food at one meal, many of them 
highly seasoned. The pleasurable taste encourages 
us to eat more than the body requires, and the result 
is frequently a loss of healthy appetite. The man who 
spends a great deal of money for his food usually gets 
less pleasure from it than the one who lives upon plain 
foods varied by an occasional luxurj^ 

Times for Eating. — Most people in this country eat 
three meals a day. In some countries four or five 



FOOD HABITS AI^D COOKING 67 

meals are the rule, in others only two or even one. 
Whatever our habit in this regard, we should eat at 
certain specified times, so that the stomach may be 
called upon to work regularly, and may also have a 
chance to rest. 

We frequently hear that candy is injurious, although 
we have learned that sugar is a useful food. The trouble 
is not with the candy, but with our abuse of it. If we 
have sweets in our possession, we are apt to be munch- 
ing them all day long, keeping the stomach constantly 
at work. Moreover, the pleasant taste of the candy is 
likely to make us eat too much, so that we suffer from 
overeating. Some people, especially children, like to be 
eating all the time. This is very unjust to the stomach. 
Continuous good health is impossible unless the stomach 
and other digestive organs are given regular times to 
rest as well as to work. 

Although breakfast is an .important meal, it need not 
be a heavy one. Nor, on the other hand, ought we to 
make too light a meal of it. This error often leads to 
headache, faintness, and weakness before the noon meal. 
Fruit, oatmeal or some other cereal, and eggs, with 
bread, form an excellent breakfast. There is no better 
drink to go with it than Avater. Milk, chocolate or 
cocoa may also be taken, but we should remember that 
they are foods as well as drinks. The heartiest meal 
should be in the middle or at the close of the day, and 
should be followed by rest of at least an hour. A little 
food before going to sleep at night helps some to rest 
easily. A glass of hot milk taken just before a person 



68 PHYSIOLOGY AND HYGIENE 

retires is frequently an excellent remedy for habitual 
wakefulness. 

The Appetite as a Guide. — When we are in need of 
food we feel hungry^ and when we need water we are 
thirsty. Hunger and thirst are, then, the guides given 
us by nature to indicate the want of food and water. 
If we treat them wisely, they guide us well, so long as 
we are in good health. But these appetites may be 
abused so that we cannot follow them safely. Some 
people, especially children, continue to eat anything 
that they happen to like particularly, even after their 
desire for food is gone, and they keep on drinking 
pleasant tasting liquids after the thirst is quenched. 
This is almost sure to do injury. 

We should eat to satisfy the desire for food. One 
who continues eating after the body has taken suffi- 
cient nourishment is intemperate. Intemperance in 
eating or drinking, which means eating or drinking 
to gratify the taste^ is probably the most common cause 
of ill health. It is always wise to stop as soon as the 
food ceases to be relished as much as it w^as when the 
meal began, instead of continuing to eat until there is 
a feeling of fullness in the stomach. If we make this 
a habit, we are not likely to suffer either from eating 
too little or too much. 

Pleasure in Eating. — The old proverb, " Laugh and 
grow fat," is a saying with sound sense behind it. 
Good temper and merriment certainly aid digestion. 
Mealtimes should be among the pleasantest occasions 
of the day. There is no reason why we should not 



FOOD HABITS AND COOKING 69 

enjoy partaking of the food, as well as take pleasure 
in the companionsliip of those wlio share our table. 
This enjoyment is lost in many homes, not only through 
making mealtimes the occasion for disputes, but by the 
unfortunate habit of '^ bolting " the food, which renders 
conversation an impossibility, and takes away all pleas- 
ure in the food itself. 

Overeating, eating rich foods in great variety, and 
eating too frequently and rapidly, are the causes of 
most of the indigestion so generally suffered. Few 
maladies occasion more discomfort than indigestion. 
When one must always ask whether this or that article 
of food will agree with him or give him pain, a great 
part of his pleasure in life is gone, and it is no wonder 
that he becomes soured in disposition, as so many dys- 
peptics do. Children usually, however, have strong 
digestive organs, and the boy or girl who will eat whole- 
some food regularly and slowly will probably have good 
digestion throughout life. 

THE HABIT OF USING ALCOHOL 

Alcohol and Digestion. — Some people try to stimulate 
digestion in various ways, most commonly by the use 
of alcoholic drinks, especiall)^ wine. Whether in cer- 
tain cases of impaired digestion alcohol may be of some 
use in stimulating tlie production of digestive juices is a 
question for the physician ; certainly for a boy or girl or 
any healtliy person to use it for this purpose is unwise. 
As an aid to digestion it should be regarded as a drug, 
and be used, if at all, only under medical direction. 



70 PHYSIOLOGY AND IIYGIP^NE 

Many persons use alcoholic drinks for this or some 
other purj)ose until they get into such condition that 
they cannot properly digest food without using wine 
or alcohol in some form, to stimulate the weakened 
digestive powers. They have become like a horse that 
will not travel without a whip. The continued use of 
the alcohol is very likely to injure the stomach so that 
finally proper digestion is impossible even with its aid. 
The boy or girl who wishes to grow up strong and 
vigorous, with healthy digestive organs, will let alco- 
holic drinks entirely alone. 

The Appetite for Alcohol. — There is one character- 
istic of all alcoholic drinks that makes them very 
dangerous. If a person eats ordinary foods, such as 
sugars and starches, he may sometimes eat too much ; 
but this does not develop a desire for larger amounts 
of the food. We may eat enough candy to make us 
ill, but it does not increase our desire for candy. On 
the contrary, it sometimes even causes us to lose all 
fondness for sweets, at least for a time. But alcohol 
frequently acts in a different way, its use creating a 
desire for more. 

The first glass a^boy takes is generally not pleasing ; 
but if he continues to use alcoholic drinks, after a little 
he comes to enjoy the taste and the effect, and in time 
he finds that he has a cj^aving for it, and feels a certain 
lack if this craving is not satisfied. Whereas at first 
a small amount of the alcoholic drink was all he wanted, 
he soon becomes accustomed to this, and almost without 
knowing it he takes a little more. This later fails to 



FOOD HABITS AND COOKING 71 

satisfy him, and, not realizing how serious a matter it is, 
he increases the amount of alcohol he uses, sometimes 
by drinking larger amounts of weaker liquors, and 
sometimes by taking stronger ones. And so the appe- 
tite grows until he finds it almost impossible to conquer 
it. In other words, instead of being a free man he has 
become a slave, and frequently a willing slave, for the 
use of alcohol constantly and in large amounts ordinarily 
destroys all desire to live a healthful, clean life. 

In most cases the boy who drinks does not know 
that the appetite is growing until it has become so 
strongly fixed as to do him great injury. In just this 
fact lies the greatest danger, for if he could realize how 
he is coming under the influence of the unfortunate 
habit, he would break it before it mastered him, and 
before it destroyed his will power. When that is gone 
the best of the boy is lost. 

Now, it is true that some people use small amounts 
of alcohol without becoming mastered by the habit. 
But it is equally true with others that the small amount 
of alcohol taken at first leads to the development of 
an appetite which in time completely masters them. 
Habitual drunkards are made out of boys and girls 
who did not intend to use alcohol enough to injure 
them. Unfortunately, even science has no way of tell- 
ing wdiich people can drink alcohol without falling 
under the sway of its appetite. Strong people, as well 
as weak, give way to it. The moment a person begins 
to use alcoholic drinks, even in a mild way, he places 
himself in the class of people from whom drunkards 



72 PHYSIOLOGY AND HYGIENE 

may be made. The only safe way is to keep as far 
from the danger as J30ssible, by letting drink abso- 
lutely alone. 

Intemperance in Eating and Drinking. — Although 
alcohol is likely to do us more harm than any other 
kind of drink or any food, still we should be careful to 
avoid all forms of overindulgeyice. We may injure our- 
selves by eating too much candy or any other enjoyable 
food. We should make up our minds to be moderate 
in all our eating and drinking, for in this way only 
can we insure the strong, healthful growth of the body, 
and only thus shall we be able to do our share of the 
world's work, unhindered by any form of ill health. 

PURPOSES OF COOKING 

No one who, on entering the house tired and hungry 
after a half day at school, has been greeted with the 
appetizing odors coming from the kitchen, need be 
told that cooking has its advantages. We eat very 
few foods without cooking, except milk, a few vege- 
tables, and fruits. Most foods are not considered fit 
to eat until they are cooked. 

There are three purposes in cooking food. 

1. Cooking develops a flavor, — We have only to 
notice the difference in taste between raw beefsteak 
and the same steak broiled and ready for the table 
to comprehend how cooking improves the flavor. It 
is true that cooking injures the flavor of certain fruits, 
such as strawberries, but it improves the taste of all 
meats and most vegetables. 



FOOD HABITS AND COOKING 73 

2. Cooking makes food easier to digest, — The cooking 
of vegetable foods is usually necessary to enable us 
to digest them. Potatoes, for example, contain large 
amounts of starch ; but it is shut up in little sacs of a 
kind of woody substance, as shown in Figure 5, and so 
long as the starch is in these sacs the digestive juices 
cannot get at it. The juices have little or no power to 
dissolve the sacs, and consequently raw potato cannot 
be digested. Cooking softens the woody sacs and sets 
the starch free. Moreover, it causes the starch grains 
themselves to burst and when burst they are more easily 
digested. We should remember that all starchy foods 
should be well cooked before they are eaten. The cook- 
ing of meats is not of great importance so far as mere 
ease of digestion is concerned. In fact, most meats are 
more easily digested if they are not cooked too much. 

3. Cooking removes danger from parasites, — Some of 
our foods contain minute living animals, called para- 
sites. Some of these, harmless in themselves, throw off 
products which are poisonous ; others are themselves 
dangerous, and might do us considerable injury if swal- 
lowed alive. Pork, especially, sometimes contains large 
numbers of very small living worms, which, if taken 
into our bodies alive, are likely to cause serious dis- 
ease, perhaps death. Pork has occasionally another 
parasite which may develop in the human stomach 
into a tapeworm several feet long. Heat kills the 
parasites, and pork, including ham, should therefore 
always be thoroughly cooked. Beef and mutton are 
less likely to contain these parasites, but neither should 



74 PHYSIOLOGY AND HYGIENE 

be eaten uncooked. We have already learned that milk 
is frequently cooked, or sterilized as we say, to destroy 
any disease bacteria it may contain. 

PRINCIPLES OF COOKING 

The ambitious girl who takes pride in her ability to 
make an appetizing cake or to prepare a dinner does 
not need to be taught the effect of cooking on the 
various articles of food. Neither does the boy who 
goes camping in the summer and gets his own meals. 
Nevertheless, there are certain principles underlying 
cooking that we cannot learn over stove or camp-fire, 
but which we can easily understand. We have already 
found by testing the white of an egg that cooking 
coagulates albumen. We know, too, from boiling 
starch, that cooking changes starch foods into pulpy 
masses. Experience in the kitchen has shown us that 
vegetables are softened by cooking, and that fatty sub- 
stances are melted or made liquid by the same process. 
In general, cooking softens foods so that they are made 
easier to chew and to digest. Another general prin- 
ciple which should be borne in mind in all cooking, is 
that proteids are coagulated by heat. This is especially 
important as related to beef tea and soups. 

Beef Tea. — If raw beef is cut fine and soaked in 
water, a part of the nutritious material is dissolved, 
and the liquid is good food as it stands. But if, 
after the beef has been soaked, the liquid is boiled, 
all of the dissolved material is coagulated and appears 
as a brownish scum. This can be separated from the 



F00J3 HABITS AND COOKING 75 

rest by straining the liquid through a cloth. Bee^f tea 
is usually strained, the liquid being used and the scum 
thrown away. Such tea is pleasant to the taste, but 
after the scum has been taken off it contains almost 
no food. Nothing is left except the salts and flavors. 
These are, however, frequently of use to invalids. The 
salts and flavors have a stimulating action on the diges- 
tive glands, and thus assist in giving the sick person 
an appetite, so that he can take, and more easily digest, 
real food. Beef tea is therefore of use in sickness or 
for persons with weak digestion ; but it should always, 
if possible, be taken together with something more sub- 
stantial. If the tea were made of finely minced beef put 
into cold water and very slowly heated, until quite hot, 
but without boiling^ it would be very nutritious, for it 
would then contain the food material, which is not all 
coagulated except when actually boiled. 

Soups and Stews. — The straining out of the food 
applies also to the making of soups from meats and 
vegetables. The heat of boiling produces coagula- 
tion, and the clear liquid, which is strained oft' and 
served as the soup, contains little more than the salts 
and flavors. Soups are not, however, usually regarded 
as foods. They are served at the beginning of a meal 
as a slight stimulant to digestion. Stews, on the otlier 
hand, the whole cooked mass of which is eaten, are 
nourishing and useful foods. Though the proteid has 
been coagulated, this does not injure the stew as a food, 
since the coagulated material as well as the liquid is 
eaten. 



76 PHYSIOLOGY AND HYGIENE 

METHODS OF COOKING 

If some one should ask us how our mothers cook, 
tlie most natural answer would be, ^^In all sorts of 
ways." The answer would be correct m a certain 
sense, and yet all kinds of cooking may be included 
under the four heads of hoiliyig^ baking^ broiling^ and 
frying. 

We put a cover on top of the kettle of boiling meat 
to hinder the escape of the steam and the odor. Simi- 
larly, whenever we can, we put a cover or crust around 
the object which is being cooked, to keep all the food 
material and flavors inside. This may be done by heat- 
ing the object very hot when the cooking begins. Thus 
a crust is formed on the outside of the loaf of baking 
bread. The high heat forms a similar protective coat 
around the meat by hardening the prot^id and so 
keeping the juices and flavors within. 

Boiling. — Boiling is one of the commonest and best 
methods of cooking, although it does not produce the 
finest flavors. The article is cooked or boiled in 
water. One of the standing rules of housekeeping is, 
'^ If you want to have the richness m the liquid^ you 
must put the article into cold water and heat slowly ; 
if you want the richness in the article itself it must 
be put into boiling water." So vegetables must be 
dropped into boiling water, while meat for stews 
should be put upon the stove in cold water. If the 
meat is placed in boiling water, a coat is formed on 
the outside at once, and then the whole may be allowed 



FOOD HABITS AND COOKING 77 

to simmer over the fire for a long time without much 
further loss. Meat cooked thus will retain its juices 
and have an excellent flavor, while the water in which 
it is cooked will contain practically nothing of value. 
The liquid of the stew, on the other hand, is to be 
eaten with the solid matter, so the meat should be 
placed in cold water and then allowed to simmer 
slowly, in order that the liquid may contain part of 
the food. Stewing is an economical method of cook- 
ing, since in this way nothing of the original food is 
lost. 

Baking or Roasting. — Baking and roasting are two 
good methods of cooking which differ slightly from 
each other, but are similar in principle. The food 
is cooked in hot air, either in an oven or over a hot 
fire. When the food is cooked over the open fire we 
call it roasting ; when cooked in an oven, w^e commonly 
speak of it as hahing^ or, in the case of meats, -we call 
it roasting. As the heat causes the liquid juices, 
especially of meat, to ooze to the surface, it is best to 
prevent the loss of these juices as far as possible. This 
is done, as in boiling, by heating the meat very hot at 
the beginning, so that a crust may be formed. The 
flavor and richness of tlie meat are much improved by 
pouring over it, say once in every fifteen minutes, the 
liquids which ooze out, a process called hast'uig. If 
there is not sufficient liquid for this purpose, melted 
butter or suet, or even salt water is used. In baking 
bread and cake it is also desirable to use high heat at 
the start. 



78 PHYSIOLOGY A:N^D HYGIENE 

BroiHng, — One of the quickest and most desirable 
Avays of cooking is broiling. Especial' care should be 
taken to begin the cooking over a very hot fire in order 
that the surface of the meat may be quickly seared 
over, and the juices thus kept in it. 

Frying. — Frjdng is a method of cooking very com- 
mon, but not wholesome. As the food is cooked in hot 
fat, butter, suet, or olive oil, it is apt to become satu- 
rated* with the fat. While fat of itself is nutritious, 
food soaked in it is very difficult to digest. To fry 
with the least injury to the food, there should be an 
abundance of fat, and it should be very hot. The high 
heat, as in other methods of cooking, forms a crust on 
the outside, which prevents, in considerable measure, 
the fat from getting into the food. 

Yeast and Baking Powder. — To make bread we mix 
flour with water, or milk, add yeast, and set the mix- 
ture in a w^arm place to ''rise." The yeast grows in 
the bread, producing a very small amount of alcohol 
and a gas called carbon dioxide. The bubbles of gas 
appear in the dough, causing it to rise up like a sponge. 
In baking, both the alcohol and the gas are driven off 
by the heat, but the bread is filled with the little holes 
Avhich were previously occupied by the carbon dioxide. 
This makes the bread ''light," and easy to masticate 
and digest. Similar bubbles are made in cake and 
biscuit by putting baking powder into the dough. As 
baking powder produces the gas very quickly, it is 
adapted to rapid baking. To develop the necessary gas 
with yeast requires that the dough rise for several hours. 



FOOD HABITS AND COOKIXG 79 



QUESTIONS 

1. Why does an Eskimo eat fish and seal, while a Chinaman 
eats rice ? 

2. What facts should be considered in choosing our diet ? 

3. What kinds of food should be used together? 

4. When should we eat ? 

5. Is food with a pleasant taste more useful to the body than 
food without flavor ? Why? 

6. How can we best enjoy our food ? 

7. Why is rapid eating unwise ? 

8. What effect has alcohol on digestion ? 

9. How is an appetite for alcohol developed? 

10. What are the purposes of cooking ? 

11. How does cooking make a potato easier to digest? 

12. What does cooking generally do to food? 

13. Why is a stew nutritious while beef tea is only a stimulant? 

14. What are the three methods of cooking? 

15. How is cooking done by boiling ? 

16. How is food cooked by baking? 

17. Why is fried food apt to be indigestible? 

18. What foods may properly be eaten without cooking ? 

19. What do yeast and baking powder do to food? 

20. Why is plain food more healthful than rich food ? 



CHAPTER IV 
CIRCULATION 

Every house in a large city is supplied with water 
from faucets. The water is carried to the house by 
pipes laid in the ground, and the pipes come from 
a reservoir which supplies the whole city. In many 
places a large pump near the reservoir forces the water 
into the pipes. If the pump stops working, the water 
throughout the city ceases to run. 

We have seen how the food which we have eaten 
gets into the blood. This food is needed in all parts 
of the body. It is carried to the arms, the head, and 
the various organs by the blood vessels, very much as 
the city is supplied with water by the water pipes. 
The blood vessels are tubes running through the body, 
dividing into branches, and these again into smaller 
branches, so that every organ of the body, no matter 
how small it may be, has at least one. The heart acts 
as the pumping station, and by it the blood is kept in 
constant motion. 

THE BLOOD 

Let us see what this liquid is which flows so con- 
stantly through the blood vessels. We already know 
that it contains the part of the food we have eaten 

80 



CIRCULATION 81 

which has been dissolved and absorbed from the intes- 
tines. But it has in it other materials besides. The 
blood that oozes from the finger Avhen we have a cut 
looks bright red. If, however, we look at it through a 
microscope, we find that the liquid itself is almost as 
clear as water. In fact, the liquid part of the blood, 
called blood plasma, is largely water, although several 
substances are dissolved in it. The red color is pro- 
duced by millions of little red bodies floating about in 
the liquid. These minute bodies are called corpuscles. 
Red Corpuscles. — The most prominent of the solid 
bodies in the blood are the red corpuscles. These are 

.^y^Red Corpuscle 
T/"/ / .. Corpuscle 

:;.:. Plasma 
^^ ;<%p^Wi-^;^^'^'^^'' Corpuscles 




Corpusde 



% 



Fig. 20. — A Little Blood, as it appears under 
A Microscope. 

shown in Figure 20. They are small, thin disks, cir- 
cular in shape. As may be seen from (7, they are slightly 
thinner in the center than at the edge. They are very 
small, only about 3-^^^^ of an inch in diameter, and 



82 PHYSIOLOGY AND HYGIEXE 

consequently they are invisible except through a micro- 
scope. They are present in the blood in immense num- 
bers, there being some 5,000,000 of them in a very small 
drop. Each red corpuscle contains a red substance 
called hemoglobin. The important work performed by 
the red corpuscles we shall study in a later chapter. 

White Corpuscles. — The white corpuscles act as the 
street-cleaners in the body. They are fewer in num- 
ber than the red corpuscles. They are transparent, 
and of a slightly bluish appearance. They have no 
definite shape, and in fact they are changing shape 
constantly, although they are most commonly some- 
Avhat spherical, as shown in Figure 20. All the cor- 
puscles, both white and red, flow through the blood 
vessels with the blood. The red corpuscles can go only 
where the blood carries them; but the white corpuscles 
sometimes crawl out of the blood vessels entirely, push- 
ing their way through the Avails. Tliey then travel 
around independently among the muscles and various 
parts of the body. There they catch and carry off 
any minute irritating substances which might produce 
trouble and perhaps disease, if allowed to remain. Thus 
the white corpuscles of the blood are believed to have 
a very important part in warding off certain diseases. 

WHAT MAKES THE BLOOD FLOW 

The Heart. — The heart is situated in the chest a little 
below the neck and slightly on the left side, where, as 
we know, its beating may be felt. In an adult, the 
heart is about the size of a man's fist, and is somewhat 



CIRCULATION 



8^^. 



To Head 



ToArm^ 



To Arm 



Artery 
(AortQ) 



±eft . , 
Auricle, 



pear-shaped, as shown in Figure 21. When in the nat- 
ural position, the apex, or small end, is turned down- 
ward and a little to the left. As long as a person lives, 
his heart continues to pump the blood through his blood 
vessels, so that the 
motion of the blood 
and of the heart 
never ceases. Like 
a pump, the heart 
has tubes entering it 
on one side bringing 
the blood in, and 
others on the oppo- 
site side carrying the 
blood away from it. 
The blood vessels 
bringing blood to 
the heart are called 
veins ; those carry- 
ing it away are called 
arteries. In Figure 
22 (facing p. 84) the 
arteries are colored 
red, the veins, blue. 

If we cut open the 
heart of some large 

animal, such as a sheep or an ox, we shall find that, 
like the human heart, it contains four cavities, as 
shown in Figures 23 and 24. The two cavities on the 
right side, called the right auricle and right ventricle, 




Aorta 



Fig. 21.— The Heart. 

Showing the veins and arteries con- 
nected with it. 



84 



PHYSIOLOGY AND HYGIENE 




Pulmonary 
'Artery 

To Lun^d 
Zemi Lunar 

Valves 



Fig. 23. 



— The Right Side of 
THE Heart. 



are connected with each other. The two on the other 
side, the left auricle and the left ventricle, are also con- 
nected with each other. There is no connection be 
^^^ ^ . tween the tw^o sides of 

the heart ; the blood can- 
not flow directly from one 
side to the other. 

As the heart beats, 
blood which has just com- 
pleted the round of the 
body, and is full of im- 
purities Avhich it has 
^ gathered, flows into the 
right auricle through the 
large veins from the head 
and body, indicated in Figure 23, and fills both the right 
auricle and the right ventricle. 
Then the heart contracts, that 
is, the muscles of the walls press 
the blood out, as we squeeze the 
juice out of a lemon by closing 
the hand tightly about it. When 
the heart contracts, the blood 
forces its way into the pulmo- 
nary artery, shown in Figure 23. 
The pulmonary artery carries it 
to the lungs to be purified. 

From the lungs the purified 
blood comes back to the heart again, this time by veins 
which send it into the upper of the two chambers at 




Fig. 24. — The Left Side 
OF THE Heart. 




2 o 



CIRCULATION 85 

the left side of the heart, that is, into the left auricle ; 
thence it goes to the left ventricle, as shown in Figure 24, 
and by this it is sent through the large artery (the aorta, 
Figs. 22 and 24) in all directions through the body. Thus 
every time the heart beats, one side of it takes blood in 
from the head and body, sending it to the lungs, and at 
the same time the other side of the heart takes blood 
in from the lungs and sends it out through the body. 

In order to keep the blood flowing in the right direc- 
tion and to prevent its flowing backward, the heart con- 
tains several valves. These are folds inside the heart. 
When open, as in Figure 23, they allow blood to pass 
freely in the direction indicated by the arrow; when 
lifted, as in Figure 24, they completely close the opening 
between the auricle and the ventricle and prevent blood 
from being forced back into the auricle when the ven- 
tricle contracts. As soon as the heart relaxes, they 
open again and allow the ventricle to fill up once more. 
There are also some valves called semilunar valves 
(shown in Fig. 23), which in a similar way prevent 
blood from flowing back from the artery into the heart. 

The Beating of the Heart. — The heart never seems to 
get tired. All day and all night our whole lives through 
it keeps at its work of pumping the blood. The heart 
of a grown person beats about seventy times a minute, 
that of a child somewhat faster. It spends about 
three tentlis of a second in beating, and tlien rests 
for four tenths of a second. In this way it really 
works less time than it rests, only instead of working 
in tlie daytime and resting at night, like the body in 



86 • PHYSIOLOGY AXD HYGIENE 

general, it does a bit of its work and then rests. In 
this way it is able to keep beating without becoming 
worn out. When w^e are in good health the heart beat 
is strong ; it weakens when we are ill. 

One reason wh)^ the use of tobacco and alcohol is 
injurious is that these substances are likely to weaken 
the proper action of the heart. Both alcohol and to- 
bacco, if used by young people, are very likely to cause 
heart difficulties. Nearly every boy knows, from his 
own observation, that neither the habitual smoker nor 
the youth who uses alcohol wins in the athletic contest. 

The Pulse. — When a stone is thrown into a pond, the 
water is disturbed in the form of a circular wave which 
grows larger and larger, but all the time lessens in 
height, until it disappears. A somewhat similar effect 
is produced by the heart as it forces the blood into the 
arteries. The wave of pressure produced by the heart 
is felt all through the arteries, though it is less strong the 
farther it is from the hearty. The wave causes a slight 
swelling of the arteries as the blood passes. The artery 
at the wrist is so near the surface that Ave can feel the 
wave, known as the pulse. 

The pulse can be found in any of the arteries where 
they are near the surface ; but as most of them are 
deep in the muscles, there are few places where we can 
feel the throbbing. The usual place for testing the 
pulse beat is at the wrist, but it can be felt at the neck, 
just under the lower jaw, and also at the temples. By 
feeling of the pulse the physician can obtain consider- 
able information regarding the general condition of the 
patient's health. 



CmCULATION 87 

BLOOD VESSELS 

Arteries. — When the bkjod is forced out of the heart 
from the left ventricle it passes into the large artery- 
shown as red in Figure 22. This serves as the main 
artery to supply the body. The artery bends over to 
the left and runs down the body, giving off several 
branches on its way. The first branches extend to the 
head and the arms, while others lead to the stomach 
and the intestines, and still others run down into the 
legs. This main artery thus supplies blood to all parts 
of the body, just as the water main furnishes water 
for every house. The farther the branching arteries 
are from the heart the smialler they become, until finally 
each is divided into thousands of minute tubes which 
enter every organ of the body. 

Capillaries. — If we should follow up a single one of 
the minute branches of an artery, we should find that it 
ends in a set of even smaller tubes, like those shown in 
Figure 25. These are called capillaries. The capillaries 
are too small to be seen except with the aid of a micro- 
scope. They divide into many branches which come 
together in a somewhat irregular manner, differing in 
different localities, as shown in the figure. The blood 
flows from the small arteries into these capillaries, and 
it is here that the food materials held in solution are 
given up to the living parts of the hodj. Every part 
of the body is filled with capillaries, and through them 
each part gets its share of food from the blood. 

We must remember that the blood, wliether in the 



88 



PHYSIOLOGY AND HYGIEIN^E 



arteries, or in the veins, or in the tiny capillaries, is 
always flowing in closed tubes. It never empties into 
the tissues, but passes to them through the delicate 
walls of the capillaries. Only the liquid part passes 
through, the corpuscles remaining in the blood vessels. 
Veins. — A four-track railroad usually has two 
tracks for the trains, say from Chicago, and tAvo for 

the trains going to 
Chicago. Let us say 
that the two tracks 
from the railroad 
center represent the 
arteries which take 
the blood away from 
the heart. After its 
journey through 
smaller arteries or 
branch roads, and 
through the capil- 
Showing their method of branching. The Jr^^j^g qj. switches 
figure on the right shows capillaries in 
the skin ; on the left, capillaries in the where it leaves the 

^^^^^^^' food, the blood is 

ready to go back to the heart on the return tracks. 

The little capillary branches combine into larger 
tubes or blood vessels called veins, which carry the 
blood back to the heart. The veins in turn combine, 
and the nearer they get to the heart the larger and the 
fewer in number they become. Finally they unite into 
two large veins, which pour all the blood back into the 
heart. Figure 22 B shows the connection of the heart 




Capillaries 



Fig. 25. — Capillaries. 



CIRCULATION 



89 



Pa!m( 
O'rculatjoi 



■i/lorzulction 



with these veins. With the next beat after the blood 
has been poured into the heart from the veins, it is 
pumped out again, and sent once more on its circuit to 
the lungs and around the 
body. The general arrange- 
ment of the heart, arteries, 
capillaries, and veins may be 
understood from Figure 26. 

The whole process of cir- 
culation, as it is called, is 
like what would happen if 
all the water that flows from 
our water faucets, and, after 
being used, is thrown into 
our sinks, were carried back 
to the reservoirs, there to 
be thoroughly purified, and 
sent out once more to the 
various houses. 

All of the arteries, except 
those going to the lungs, 

carry pure bloody while the Fig. 26. — A Diagram showing 

veins, except those coming ™''' ^^"'^""^'^ Cikcilxtiox. 

The blood flows in the direction 
from the lungs, carry im- of the arrows. 

pure blood. The pure blood 

becomes impure as it takes up waste material in tlie 

capillaries, as explained in a later chapter. 

The arteries are embedded deeply in the flesh : the 

veins are nearer the surface. A cut in the flesh is 

almost sure to sever one or more small veins, but 




llcnes 



90 PHYSIOLOGY AXD HYGIENE 

unless it is very deep the arteries will not be injured. 
The blue lines appearing on the back of the hand, 
when the hand is allowed to hang downward, show 
the positions of the veins. 

HOW THE BLOOD FLOWS 

Most of us are familiar Avith some form of pump. 
We have noticed that the water flows out of the spout 
in spurts ; but if it is allowed to pass for some distance 
through a trough or along the ground, it flows as 
steadily as if it had come from the pump in a contin- 
uous stream. The movement of the blood in our 
bodies is similar. The heart sends the blood into 
the main artery in spurts, pumping it with force, just 
as the pump forces Avater into the trough. As the 
blood goes farther and farther from the heart, it flows 
along more quietly, until, by the time it has passed 
through the capillaries and is on the home trip through 
the veins, the spurting has ceased entirely. 

When the heart beats, it forces more blood into the 
arteries than can easily flow through them. Instead of 
being stiff, however, like iron Avater pipes, the arteries 
are elastic like India rubber. The blood flowing into 
them in spurts causes the arteries to stretch, so that 
it floAVS more smoothly than it AA'Ould if flowing in 
similar spurts through iron pipes. 

Bleeding. — The blood is pumped into the arteries 
Avith so much force that it floAVS out A-ery rapidly in 
strong jets if an artery is cut or broken. The bleed- 
ing must be stopped quickly, or the person may bleed 



CIRCULATION 



91 



to death. The veins, on the other hand, do not become 
stretched, since the blood flows in them with less force. 
If a vein is cut, the bleeding is not so rapid as from a 
severed artery, and it is not so dangerous. But in 
any case the bleeding must be stopped, for even a 
small wound in a vein would cause death if the flow 

of blood were 

not checked. 
Many of the 




■■■•Artery 



most common 
accidents to 
which we are 
liable produce 
bleeding. If the 
wound is only a 
slight break or 
a cut in the 
skin, the bleed- 
ing will not be 
serious. We 



rront 
View 




Fig. 27. 



Showing need only to Pj(. 28 
THE Main Artery i - ,i t 

OF THE Arm. bring the edges 



Showing 
THE Main Artery 
IN THE Leg. 



In front of the leg 
above the knee, but 
behmd it below the 
knee. 



together and 
bind the cut or other wound some- 
what tightly with a cloth or a bit 
of adhesive plaster, and the bleed- 
ing soon stops. Even wounds which are comparatively 
deep will usually stop bleeding, if they are tightly 
bound and held quiet for a time. 

Bleeding from Arteries. — An artery wound is more 



92 



PHYSIOLOGY AND HYGIENE 



serious, and must be treated promptly in order to save 
the person's life. If a cut or Avound of any sort is 
followed by a forcible spurting of blood, it is certain 
that an artery has been cut. The only way to stop the 
bleeding is to compress the artery above the cut^ that 
is, between the cut and the heart. Severed arteries are 
most common in the arms and the legs, and the treat- 
ment in such cases is simple. Figures 27 and 28 
show the course of the chief arteries 
in the arm and the leg. Figure 29 
shows a simple method of grasping 
the arm so as to compress the artery 
and stop the bleeding, temporarily, 
anywhere in the arm below the 
elbow. 

The easiest and most effectual 
method of stopping the flow is, 
however, to put a bandage or liga- 
ture around the arm above the cut, 
and to place a stick inside it, as 
HOW TO COMPRESS iudlcatcd in Figure 30. The stick 

THE Arm to stop -^ ^j^^^ ^^ |^^ turned, twisting the 
Bleeding. ' ° 

bandage, and binding the arm 

more and more tightly, until the bleeding stops. 

If a stone or a tightly rolled handkerchief is placed 

under the ligature and over the artery, less pressure is 

required. A physician must then be summoned as soon 

as possible. The ligature must be kept in position 

until the physician can tie the artery and prevent 

further bleeding. With a wound in the leg the 




Fig. 29. — Showing 



CIRCULATIOX 



93 



method of stopping the floAV of blood is similar. 
Prompt action is of supreme importance in all such cases. 

Why the Bleeding stops. — If there is a break in the 
water pipe laid along a city street, the water continues 
to flow out until the workmen have repaired the pipe. 
The leaking would never stop 
of itself. How is it then that 
bleeding from a vein stops 
itself, or can be stopped, so 
readily ? If, whenever there 
was a break in the pipes, the 
water should freeze a short 
distance above the break, the 
ice would close up the open- 
ing and stop the leak. Some- 
thing of this sort really occurs 
in the case of a wound. The 
blood does not freeze, of 
course, but it becomes some- 
what solid; a change takes Fig. 
place in it which we call 
clotting. 

Blood Clotting. — Blood, as we know, is a liquid. If 
blood be drawn into a small dish, it will at first be 
liquid, like water. But if it is allowed to stand for a 
few minutes, it stiffens, becoming somcAvhat jellylike. 
The hardening continues until the blood is changed into 
such a firm jelly that it will not flow out, even if 
the dish is turned upside down. In otlier words, the 
blood has clotted^ as is shown in Figure 31. A great 




30. — Showing the 
Method or applying a 
Ligature. 



94 



PHYSIOLOGY AND HYGIENE 



change has been produced in the nature of the blood, 
and after clotting it would naturally be of no further 
use, as it could no longer flow through the blood vessels. 
If blood is taken out of the blood vessels, it always 
clots in a very few minutes, no matter whether it 
is heated or cooled, or whether it is brought in con- 
tact with the air or not. So long as it remains inside 




Blood 



Fig. 31. — Showing the Clotting of Blood. 
At J. it is liquid ; at jB it is solid. At (7 it is partly liquid again. 



the blood vessels it continues in liquid form. If, how- 
ever, the blood vessels themselves are injured by a cut 
or bruise, the blood begins to clot rapidly near the 
wound. 

From this fact we learn how bleeding is stopped. 
Whenever a bruise or a cut breaks a blood vessel, 
the wound at once begins to bleed. But the injury to 
the blood vessel causes a clotting in the blood near the 
bruise, and the clot soon closes the wound. As a result, 



CIRCULATIOX 95 

any ordinary wound soon ceases to bleed; but if there is 
a large cut through a vein or an artery, the blood may 
flow out so rapidly that it does not have time to clot. 
In such cases the bleeding must be stopped by a ligature 
or some other artificial means. 

Effect of Gravity. — If we hold the hand downward 
for a few minutes, it becomes red, because it is filled 
with blood. If, on the contrary, the hand is held 
above the head, it turns whiter. This shows us that 
the blood flows down more easily than it flows up. 
Of course, the blood in flowing through the blood ves- 
sels, is pushed on by the force of the heart. Even 
when the blood flows downwards into the legs, it must 
be pushed by the beating heart. But the weight of 
the blood itself has some influence upon its flow, helping 
the heart to send the blood down, and holding back, 
more or less, the upward flow. The aiding and checking 
of the flow by the weight of the blood, or gravity, is, 
however, of no practical importance except under cer- 
tain conditions, such as fainting. 

Fainting. — Fainting is commonly due to lack of sufti- 
cient blood in the brain. This causes unconsciousness. 
Recovery from the fainting fit occurs as soon as the 
necessary amount of blood is restored to the brain. 
When a person faints it usually means that the heart 
is not beating vigorously enough to force the blood 
upward to the brain. We should, accordingly, assist 
the heart by placing the liead of the patient a little 
lower than the body. This will help the blood to run 
into the head from its own weight. The return of blood 



96 PHYSIOLOGY AND HYGIENE 

to the brain may also be hastened by stimnlating the 
action of the heart. Dashing a little cold water upon 
the face hastens the beating of the heart, helps to re- 
store the blood to the brain, and so insures recovery 
from the fainting fit. Our natural impulse, when a 
person faints, is to lift his head, but as a rule this will 
hinder recovery. 

HOW THE FLOW OF BLOOD IS CONTROLLED 

Regulation of the Heart Beat. — The circulation of the 
blood is produced by the beating of the heart, and at 
the same time the heart is partly controlled by the 
brain. The heart can be entirely removed from the 
body of a cat or a dog and yet it will continue to beat, 
sometimes for hours. This shows that the heart is 
able to beat independently of the brain. Nevertheless 
the brain has the power of hastening and checking the 
heart's action. The brain is, in fact, the central organ of 
the body, and as such it controls the action of every part. 

Passing from the brain to the heart are two nerves 
which serve, like telegraph wires, to connect the two. 
Over these nerves the brain is constantly sending mes- 
sages to the heart. Sometimes the heart beats more 
rapidly than is necessary, and the brain sends a message 
which checks its action a little and makes it beat more 
slowly. At other times the heart does not beat fast 
enough, and needs to be hastened. If, for example, a 
boy starts to run, he needs to have an extra amount 
of blood sent to the muscles. Immediately the brain 
sends a message that sets the heart to beating faster. 



CIRCULATION 97 

which, of course, causes the blood to flow more rapidly. 
After the boy stops running, at the brain's command 
the heart beat becomes gradually slower until it reaches 
the ordinary rate. There are many other occasions 
when a quickened heart beat is desirable. 

The brain seems in every case to recognize the need, 
and controls the heart accordingly. All this is done 
without any thought on our part. We cannot by will 
power change the rate of the heart's beating, and usually 
we do not even know when a change occurs. 

We can readily test the difference in the rate of the 
beating by counting the number of beats a minute, 

(1) after we have been sitting quietly for some time, 

(2) after we have walked up a flight of stairs or have 
run for some distance, and again (3) after fifteen min- 
utes of quiet. 

Regulation of the Blood Vessels. — The flow of water 
from the city water pipes is regulated in two ways. 
The pump may work more or less rapidly as occasion 
demands ; the faster its movement, the greater the 
amount of water flowing into the pipes. This action 
corresponds to the changes in the rate of the heart beat. 
The flow of water in the various houses depends upon 
how wide we open the faucet, whether to its full extent, 
halfway, or not at all. So in our bodies there is a 
means of changing the size of each little blood vessel, to 
allow either more or less of the blood to pass through. 

All of the small arteries have muscle fibers running 
around them, as indicated in Figure 32. When these 
muscle fibers contract, they narrow the blood vessel, 



98 



PHYSIOLOGY AND HYGIENE 




EiG. 32. 



- Section of an Aktery and 
A Vein. 



Showing the thick elastic wall of the 
artery and the thinner wall of the vein. 



lessening the amount of blood allowed to pass. When 
they relax again, the blood vessel opens and the blood 

flows in a larger 
stream. These mus- 
cle fibers are all con- 
nected with the brain, 
or the spinal cord, by 
nerves through which 
they can be made to 
relax or contract. In 
this way the flow of 
blood in any organ of 
the body can be in- 
creased or decreased. 
If for any reason a particular part of the body needs 
more blood than usual, it is not always necessary to 
increase the rate of the heart beat. The little muscles 
around the arteries simply relax, so that these blood 
vessels become larger, and at once more blood flows 
through them. On the other hand, if less blood is 
needed in a certain organ, the brain causes the muscle 
fibers to contract, so as to close, or partly close, the 
blood vessels. 

When any part of the body is actively at work, it 
needs plenty of blood, since the blood brings it nourish- 
ment. The more vigorous the work, the greater is the 
amount of blood needed. The brain needs an extra sup- 
ply when we tliink hard, the leg muscles when we run. 
After a hearty dinner the stomach and the intestines 
need a large amount of blood for the work of digestion. 



CIRCULATIOX 99 

By means of the nerves from the brain (vaso-motor 
nerves, they are called), the small arteries in the intes- 
tines are made to relax and allow the blood to flow 
through more quickly than usual. The Avails of the 
intestines and the stomach become filled with blood, 
and digestion goes on rapidly. 

This large flow through the intestines necessarily 
draws some blood from the brain and other parts of 
the body. Accordingly, after a heavy meal most people 
are a little stupid and rather inclined to sleep. On 
the other hand, when a person is studying very hard, 
so that the brain is especially active, the blood vessels 
in the brain itself are relaxed to allow of a large flow 
of blood. It is therefore difficult to do profitable 
studying and to digest a heavy meal at the same time. 
Either the brain will take too much blood to allow of 
good digestion, or else tlie stomach and the intestines 
will have so large a share of the blood that the brain is 
sluggish and the lessons suffer. 

Blushing results from a similar action of the blood 
vessels in the skin of the face ; these vessels are relaxed, 
and allow an extra amount of blood to flow through 
them. The cheeks become thereby red and warm. On 
the other hand, an unusual contraction of the vessels 
in the face causes the skin to become pale. A flushed 
skin thus means expanded blood vessels, Avhile a pale or 
ivMte skin means contracted ones. 

The Feeling of Warmth and Cold. — The expansion 
and contraction of tlie small arteries in the skin cause 
our feelinofs of heat and cold. The blood is warmer in 

LcfC. 



100 PHYSIOLOGY AXD HYGIENE 

the interior of the body than at the surface, but since 
only the skin feels warm or cold, Ave do not notice 
the warmth of the blood as long as it is below the skin. 
When we exercise vigorously, as in running, we feel 
very warm. The reason is that the exercise causes the 
blood vessels in the skin to expand so that an extra 
large amount of blood flows through them. The skin 
becomes red and the blood so warms it that we feel 
the heat. 

Although we feel especially warm when the blood 
flows rapidly through the skin, the body is in fact no 
warmer than usual. Indeed, the sending of the warm 
blood through the skin is the means by which the body 
cools its blood, to keep us from really becoming warmer. 
If the body seems likely to become too warm, it sends 
blood to the skin at once, to be cooled by the air. But 
if the body has too little heat, the blood vessels con- 
tract, and the warm blood is kept away from the sur- 
face, causing pallor of the skin. The skin blood vessels 
thus serve much the same purpose as little windows, 
which are opened or closed to regulate the temperature. 

Sometimes we are deceived by the feeling of warmth. 
Whenever the blood vessels in the skin are opened wider 
than usual, so that warm blood flows through them, we 
may be sure we are cooling off, no matter how warm we 
feel. Now there are certain substances which, if taken 
into the stomach, cause the blood vessels to enlarge. 
For example, a certain amount of alcohol causes the 
skin to become flushed and the body to feel warm. 
Many people believe, therefore, that the alcohol has 



CIRCULATION 101 

actually warmed them, and so they take it on a cold 
day to keep them warm. Exactly the opposite is the 
case. The alcohol has caused the blood yessels to 
expand, or, in other words, it has opened the windows 
in the skin, and the body has begun to cool. The 
person feels warm simply because the skin is heated, 
but he is really losing heat more rapidly than before. 
Arctic explorers find that they cannot endure the 
extreme cold so well if they use alcoholic drinks. 

We should never use any form of alcohol from a 
belief that it warms the body and helps us to endure 
the cold. Sometimes, after a person has been overcome 
with cold, and is half frozen and perhaps unconscious 
from the exposure, alcohol may be given as a stimulant 
to quicken the action of the heart and hasten recovery. 
Under such circumstances it is not used to warm the 
person, but for its stimulating effect. 

SUMMARY OF THE CIRCULATION PROCESS 

Let us trace briefly once more the journey made by 
the blood, beginning when it enters the heart after a 
journey around the body. It enters the right auricle 
and ventricle of the heart through large veins coming 
from the head and body. Then it is forced into the 
pulmonary artery, which carries it to the lungs to be 
purified. From the lungs it returns to the heart, this 
time entering the left auricle and ventricle, from which 
it passes into the main artery of the body. The main 
artery divides into branches whicli take blood to the 
head, the limbs, and the various organs; and the 



102 PHYSIOLOGY AND HYGIENE 

branches subdivide into smaller and smaller branches 
which finally end in the little tubes called capillaries. 
There the pure blood gives up its food, and at the same 
time takes up the waste products. 

From the capillaries the impure blood enters small 
veins which connect with larger veins, and these with 
still larger ones, until finally all unite in the two 
large veins which carry the blood to the heart once 
more. 

The beating of the heart is continuous, but the rate 
can be increased or diminished through the action 
of the brain; and the blood supply of any organ can be 
increased or diminished by the expansion or contrac- 
tion of the small blood vessels. The whole circulation 
is controlled without our being conscious of the fact or 
being able voluntarily to change it in any way. 

QUESTIONS 

1. What is the purpose of circulation? 

2. Describe the red blood corpuscles. 

3. What is the use of the white blood corpuscles? 

4. What is the duty of the heart ? 

5. What are arteries ? Yeins ? 

6. Do any of the arteries carry impure blood ? 

7. How can we tell when an artery is cut? What should be 
done in such case ? Why is such a cut more serious than a cut 
vein ? 

8. How does nature stop bleeding from wounds? 

9. If the blood would not clot, what would happen when a per- 
son is cut? 

10. What is the pulse ? Why does a physician count a patient's 
pulse ? 



CIRCULATION 103 

• 

11. What are the capillaries? 

12. What is fainting? What is the remedy for it? 

13. How is the flow of blood regulated ? 

14. How is the amount of blood that each organ receives regu- 
lated? 

15. Why should we not study immediately after a hearty dinner ? 
16.- If a person should run rapidly immediately after dinner, 

would it help or hinder digestion? Why? 

17. Why do we feel warm after running ? 

18. Why is it that alcohol makes a cold man feel warmer? Is 
he actually warmer ? 



CHAPTER V 
RESPIRATION 

Only as the fuel in a locomotive is burned does it 
drive the engine. The burning of the fuel is really a 
union of the coal with a certain part of the air called 
oxygen. The process is oxidation, and it produces heat. 
As a result of the burning, a large amount of another 
gas, carbon dioxide^ is produced, which passes out of 
the smoke-stack with the smoke, and there is left 
in the grate a quantity of ashes. In order that the 
fires in the engine may be kept burning brightly, it is 
necessary that there be a supply of air. This is fur- 
nished by means of the draft. It is necessary also 
that the gases have some means of passing off, as they 
do through the smoke-stack. The ashes must also be 
frequently, removed from the grate to keep the fires 
free, and allow the air to reach the burning coal. 

The processes which take place in our bodies are 
somewhat similar to those in the engine. The food is 
oxidized^ although the process differs much from the 
burning of coal, and a certain amount of heat is pro- 
duced which warms the body. Oxygen gas from 
the air is as necessary for the body oxidation as for 
burning the coal. What is more, there is produced in 
the body the same kind of gas as in the engine, carbon 

104 



RESPIRATION 105 

dioxide, and a certain material is left that corresponds 
in a way to the ashes, and of this the body must dis- 
pose. How the body gets its oxygen, and gets rid of 
its carbon dioxide, is a story in itself. This exchange 
of gases between the air and the blood is brought about 
by breathing, or respiration. 

THE AIR PASSAGES AND THE LUNGS 

When we breathe properly, air is taken in at the nos- 
trils, and after passing through the large nasal cavities 
above the mouth enters the throat. The nostrils, as we 
saw in Figure 12, lead directly to the throat, so that the 
air has a free passage. We have seen, too, that the 
mouth also leads directly to the throat. If the mouth 
is open, air may be taken through it even more easily 
than through the nostrils. In either case the air passes 
directly into the throat, and then down to the lungs. 

Mouth-hreatliing is not, however, the natural method 
of taking in air, and is always injurious if continued 
for any length of time. The air passes much more 
rapidly through the mouth than through the nostrils, 
and consequently it is not so thoroughly warmed when 
it reaches the lungs. What is more, the dust in the air 
is not so completely removed as when it passes through 
the nostrils. The narrow, irregular passages of the 
nose, with their moist surfaces and hairs, hold the dust 
and prevent it from passing into the lungs. We should 
carefully avoid getting into the habit of breathing 
throuHi the mouth, even when walking' fast or wlien 
running, lest we cause throat and luno- troubles that 



106 PHYSIOLOGY AXD HYGIENE 

may be a serious menace to health. If a person should 
find that he really is unable to breathe excepting with 
the mouth open, it indicates that sometliing is wrong 
in his throat or nose, and he should be examined by a 
physician. 

The Windpipe or Trachea. — The air passes from the 
throat into the windpipe (see Fig. 12). This is a large 
tube at the front of the neck. As we have seen, it is 
always open, except that at the instant when food 
is being swallowed the epiglottis closes down over 
it like a lid. The epiglottis springs up again, how- 
ever, as soon as the food has slipped by, to allow the 
free passage of air to and from the tube. The wind- 
pipe itself is held open by a series of hard, cartilage 
rings in its walls, which prevent it from collapsing. 

Just within the upper end of the windpipe is situated 
a very important organ, the larynx. If we place our 
fingers upon the outside of the throat just below the 
jaw, we can feel a hard bunch move up and down as we 
swallow. This bunch, sometimes called the Adam's 
apple, is the larynx. Figure 33 shows its location at 
the beginning of the windpipe. Inside of the larynx 
are the so-called vocal cords, by means of which we are 
able to make sound when talking. Below the larynx 
the windpipe passes down through the neck in a 
straight line and enters the chest, where, as shown in 
Figure 33, it divides into two branches. 

The Lungs. — When the windpipe divides, one branch 
enters one of the lungs, and the other branch enters the 
other lung. The lungs look like two elastic bags, as 



RESPIRATION 



107 



indicated in Figure 33, and are capable of being dis- 
tended when air is drawn in, and of collapsing when 
the air is expelled. Each of the bags seems to be filled 
with a mass of spongy material, which is made up prin- 



,Marynx 



Air 




Fig. 33.- 

Upon the left is shown the hmg from the outside ; 
upon the right the lung is opened to show the 
branches of the air tubes. 

cipally of air tubes, air cells, and blood vessels. Each 
branch of the windpipe, on entering the huig, divides 
into numerous smaller branches. Each of these divides 




108 PHYSIOLOGY AND HYGIENE 

again, and so the division continues, until finally the 

smallest of the branches form a system of very minute 

tubes similar in its irregular divisions to the twigs of a 

tree. The whole lung, in fact, appears somewhat like 

a tree with the branches upside down. Each twig ends 

in a small rounded sac or air chamber. The air taken 

in through the nostrils finally enters and expands these 

little chambers, which are shown in 

Figures 33 and 34. The lungs 

contain many thousands of the 

sacs, and every time we breathe 

they expand with the air wdiicli 

they take in. Thus the whole lung, 

^ir5acs being filled with air, is light and 

Fig. 34. —Air Sacs, spongy. It is an excellent plan 

Found at the ends of the tx) draw several long breaths every 
air tubes in the lungs. 

little while, to distend the air sacs 

as much as possible, thus '' clearing the lungs " as 

we say. 

Blood Vessels of the Lungs. — We have already learned 

that the right side of the heart receives the impure 

blood and sends it through the pulmonary artery to the 

lungs. When this artery enters the lungs it divides 

and subdivides into small blood vessels, wdiich in turn 

divide into very small capillaries. The capillaries are 

wrapped around the air sacs, appearing like a sort of 

net about them (Fig. 35). While the blood from 

the heart is flowing through the capillaries it is very 

close to the air which fills the sacs. It is so close, in 

fact, that it takes some of the oxygen out of the sacs. 



RESPIRATION 



109 



giving up to them in exchange the impure gases which 
it holds. After leaving these gases and taking the 
oxygen, the blood is purified and ready to go back to 
the heart. 



HOW AIR IS DRAWN INTO THE LUNGS 

When the handles of a pair of bellows are extended 
the cavity inside is enlarged, and air is sucked in to fill 
the increased space. 
If a rubber ball with 
a hole in it is com- 
pressed until it col- 
lapses, and is then 
held in a dish of 
water and allowed 
to take its normal 
shape, the hollow 
fills with water. 
Breathing is based 
upon a similar prin- 
ciple. The air is Fig. 37. — Showing the Chest with the 
drawn into the ^"''''^ ^'^^ ^"^''^ '" ^'^^'"^^ ''^"'^" 

THE Ribs. 
lungs in much the 

same way that bellows are filled with air and the ball 

is filled with water. 

The Chest or Thorax. — The lungs are incUised in a 

box called tlie chest. This is closed in front, at tlie 

sides, and at the top by the ribs, muscles, and skin. 

Figure 37 shows the chest and the position of the lungs. 

At the rear the chest is closed by the backbone and 




no 



PHYSIOLOGY AND HYGIENE 



the ribs. A thin muscular partition, the diaphragm, 

stretches across the bottom, shutting the box up com- 
pletely. The windpipe is the only opening in the chest 
for the entrance of air. 

The position which the diaphragm would take if left 
to itself is that of a slight upward curve, as shown in 

Figure 38. Each time we 
draw in a breath, the muscles 
of the diaphragm shorten and 
draw it down to the posi- 
tion shown by the dotted line 
in Figure 38. This enlarges 
the space in the chest, and 
the outside air, rushing in 
through the nostrils and the 
windpipe, enters the lungs, 
and fills the enlarged space. 

The diaphragm is helped 
by the ribs in making the 
space within the chest larger. 
The ribs, in their usual posi- 
tion, tend to bend downward. 
As we breathe, the numerous 
muscles surrounding the ribs 
Fig. 38. — Showing the Move- ^^^ise them upward and f or- 

MENT OF THE DiAPHEAGM IN ward, incrcasiug considerably 

Breathing. . ' 

.^^ -, ^, , ,. ^ ^, the space withm. 1 he dotted 

The dotted line represents the ^ 

position at the end of an lines in Figure 39 show the 

inhalation. position of the ribs when the 

lungs are full. Air is drawn in when w^e breathe simply 




RESPIFtATION 



111 



because of the enlargement of the cavity of the chest 
which sucks air in through the nostrils, much as it is 
sucked into a pair of bellows. 

After the lungs are thus filled with air, the muscles 
relax, and the ribs fall of their own weight into the 
position shown in the solid 
lines of Figure 38. At the 
same time tlie diaphragm re- 
laxes, and is pushed up to its 
former position, partly by its 
own elasticity and partly by 
the organs below, which it had 
previously compressed. Both 
motions decrease the size of 
the chest cavity, and the air 
is squeezed out exactly as 
the air is forced from the bel- 
lows by the pressure on the 
handles. Drawing the air into 
the lungs is called inspiration 
or inhalation. Forcing tlire air 
out by contraction is called 
expiration or exhalation. The 
whole process is controlled 
through nerves by the brain. 

Capacity of the Lungs. — A 
certain amount of air is 
drawn into the lungs with each 
breath, and about the same amount forced out. 
the lungs are never completelj^ lilled by an ordinary 




Fig. 39. — Showing the 
Movement of the Ribs 
IN Breathing. 



But 



112 PHYSIOLOGY AND HYGIENE 

breath, nor are they ever completely emptied after the 
exhalation. After taking an ordinary breath we can 
still breathe in more air by an additional deep breath, 
and after an ordinary exhalation we can expel more air 
by an effort. Thus in ordinary breathing we change 
only a part of the air in the lungs. In fact, the lungs 
of a grown person commonly hold about 350 cubic 
inches of air, of which only about 30 inches are changed 
with each ordinary quiet breath. We might renew 
most of the air by very rapid and very deep breathing, 
but to do so continuously would be too great an effort. 

Lung Exercise. — The lungs should by all means be 
completely filled with pare air occasionally. If the air 
in the little air sacs is seldom changed, but remains 
more or less stagnant, the sacs furnish excellent lodg- 
ing places for dangerous bacteria, and they may even 
be the starting point for consumption, pneumonia, or 
some other lung disease. If people exercised the air 
sacs more vigorously, filling them constantly with fresh 
air, the danger of lung trouble would be decreased. 

How shall we give our lungs the needed exercise ? By 
drawing long, deep breaths, filling the lungs as full as 
possible, and then blowing out the air slowly and forci- 
bly. If we acquire a habit of frequently filling the lungs 
deeply with fresh out-of-door air, we shall strengthen 
them, increase their capacity, and improve our general 
health. Persons whose work is such as to produce vig- 
orous activity of the lungs do not need such special 
exercise. If one is obliged to walk up a steep hill 
daily, so that he becomes somewhat breathless, the lungs 



RESPIRATION 113 

receive all the exercise needed to keep them properly 
active. The active boy or girl ordinarily gets jjlenty 
of lung exercise in play. It is important to remember, 
however, that with the quiet life which many persons 
live, especially in our cities, the lungs need special 
exercise to make them strong and to give them the 
amount of fresh air necessary for health. 

WHAT BREATHING DOES FOR THE BLOOD 

How Blood is changed in the Lungs. — The blood 
which enters the lungs to be purified is very different 
from the blood which returns from the lungs to the 
heart. Four important changes occur in the lungs. 

1. The blood takes up oxygen from the air, — The red 
corpuscles have the power of taking up oxygen from 
the air. Each one of the millions of these corpuscles 
takes from the air in the lungs as much of the oxygen 
as it can hold. As soon as the oxygen has been 
absorbed, the corpuscle becomes a brighter red than 
before, and consequently the blood itself is of a more 
brilliant color. The blood that flows into the lungs is 
bluish red ; the blood that comes out is bright scarlet. 

2. The hlood gives up carlon dioxide gas, — The car- 
bon dioxide gas leaves the blood, enters the air in the 
lungs, and is then expelled in the exhalation. 

3. The hlood is cooled. — The blood is somewhat 
cooled while it is flowing tlirough the lungs. The air 
which we breathe into our lungs is usually cooler than 
the body. In an ordinary schoolroom it is about 70°. 
But the same air when expelled from the lungs is nearly 



114 PHYSIOLOGY AND HYGIENE 

as warm as the body (about 98°). It has been warmed 
in the lungs by the blood, the blood itself being cooled 
at the same time. 

4. The blood loses some of its ivater in the lungs. — If 
we breathe upon a cold windowpane, little drops of 
water collect, making the glass cloudy. These drops 
condense from the moisture we exhale. The air 
breathed from the lungs is usually nearly saturated 
with vapor. When we walk out of doors on a cold 
winter's morning, we can ''see our breath"; that is, 
the water in the breath condenses into a slight fog 
as it comes from the mouth or nostrils. This water all 
comes from the blood. Thus the blood on leaving the 
lungs contains less water than when it enters. 

How the Oxygen is Used. — After the blood has taken 
the oxygen from the air in the lungs, it goes directly to 
the left side of the heart. From there, as we have 
already learned, it is sent to all parts of the body 
through the arteries, finally reaching the capillaries. 
The blood flows through the capillaries very slowly, 
and here each red corpuscle lets go of the oxygen it 
took while in the lungs. The oxygen passes at once 
from the blood to the tissues of the body around the 
capillaries. The red corpuscles are thus the oxygen 
carriers. They go to the lungs, seize the oxygen, and 
then carry it to every part of the body needing it. 
After they have given up the oxygen they become 
bluisli red, so that the blood which leaves the capil- 
laries to go back through the veins to the heart is a dark 
bluish red. 



RESPIRATION 116 

We have already seen that the oxygen is brought 
into the body to unite with the food, just as it unites 
with the fuel in a locomotive, and that as a result 
there is produced the waste gas, carbon dioxide. 
While the blood is passing through the capillaries, it 
not only gives up oxygen to the tissues but it takes 
from them the carbon dioxide Avhich has been pro- 
duced. Thus when it comes back from the tissues to 
the heart, the blood is carrying carbon dioxide in the 
place of the oxygen. Such blood is called venous hlood^ 
and is said to be impure because it contains waste prod- 
ucts. When this blood reaches the lungs again it gives 
off the waste carbon dioxide it is carrying and gets 
another load of oxygen. 

Respiration is then an exchange of gases betiveeji the 
body and the air. The blood is all the time passing 
through the lungs where it gives up carbon dioxide, 
water, and other gaseous waste products and takes 
oxygen. Going thence to the various parts of the 
body, it supplies them with the oxygen and takes away 
the carbon dioxide. If anything hinders breathing, 
there is trouble, for the same reason that a fire will 
not burn unless there is a draft to furnish air to the 
burning coal. If breathing stops for more than a few 
minutes death follows, since the body is tlien unable 
to obtain oxygen or get rid of waste gas. 

Breathing and Exercise. — We can readily under- 
stand why, if we exercise vigorously, the rate and the 
depth of breathing Avill be increased. If an engine is 
to work rapidly, it must have a good draft, and it must 



116 PHYSIOLOGY AND HYGIEXE 

burn large quantities of coal ; a large amount of ashes 
will be left, and a great deal of smoke will issue from 
its chimney. So with our bodies. If we are to work 
our muscles vigorously, we must have a large supply 
of oxygen to oxidize the necessary food, and an in- 
creased amount of waste will be produced. The blood 
must consequently flow faster than usual, both to 
furnish the oxygen and to carry off the waste. To 
accomplish this the heart begins to beat faster so as to 
increase the speed of the blood, and at the same time 
our breathing becomes more rapid, so that the rapidly 
flowing blood may be supplied with oxygen, and all 
the waste may be carried away. 

VENTILATION 

Need of Ventilation. — It is evident that we need a 
great deal of pure air. The rooms in which we live 
should be well ventilated. There are two purposes 
in ventilation : 1. To furnish us with a sufficient supply 
of oxygen; 2. To provide air that can carry off dust, 
noxious gases, and moisture. 

Anything which uses up the oxygen in a room, 
or which allows too large an amount of breathed air 
to accumulate, renders the air unwholesome. If a 
great many people are breathing the air in a room, 
or if gas or oil stoves or lamps are using up the oxygen 
and giving out carbon dioxide, the air, unless changed, 
becomes oppressive and poisonous. In such cases it is 
especially necessary to attend well to the matter of 
ventilation. 



EESPIRATION 117 

Evils of Indoor Life. — People who live in warm 
climates spend much of their time out of doors. We 
in the colder climates have formed the habit of living 
in close rooms, where we remain for hours at a time. 
In the close rooms we are often forced to breathe over 
and over the air which has already been breathed by 
ourselves or other people, and this is most unwhole- 
some. The habitual breathing of impure air is partly 
the cause of some of the lung diseases, as pneumonia 
and consumption. This does not mean that people 
living out of doors never have lung troubles ; but such 
diseases are most common among those who live in 
close rooms. City workmen, though better fed than 
country workmen, are usually less healthy. If w^e 
could be in the open air most of the time, we should 
avoid many of these difficulties ; but since in cold 
climates this is not pleasant in winter, we must at least 
keep our rooms supplied with plenty of fresh air. 

The Need of Fresh Air. — Many people arrange their 
living rooms with a wholly mistaken idea of what is 
healthful. They seem actually afraid of fresh air. So 
careful are they to prevent drafts that they exclude 
fresh air. They think that they take cold because tlie 
rooms are not warm enough, or because of changes in 
temperature, so they keep the air as uniformly warm 
as possible. Probably more colds are due to over- 
heated or impure air than to drafts or cold air. We 
take cold from drafts frequently because we accustom 
ourselves to liidng in warm rooms. A temperature of 
from 65° to 70°, depending upon how actively we are 



118 PHYSIOLOGY AND HYGIENE 

employed at the time, is the proper temperature for 
living rooms in cold weather. 

A very large class of people consider night air 
especially dangerous, and for this reason they sleep in 
rooms closed up tightly, to prevent fresh air from 
entering. Night air is no more injurious than day 
air, except that it is likely to bring mosquitoes, which 
should be kept out of the sleeping room ; and there 
is no time when a person should be more partic- 
ular that the air is pure than when he sleeps. The 
attempt to shut out night air from sleeping rooms is a 
grave mistake, and this is true both in winter and in 
summer. Fresh air is one of nature's best remedies 
for many diseases. If we determine to make it a 
point through life to breathe plenty of wholesome, fresh 
air, we have laid a firm foundation for vigorous health. 

How Rooms are Ventilated. — More or less fresh air 
gets into the rooms of an ordinary dwelling house, no 
matter how tightly they may be closed. If a stove is 
used in a room, the fire causes a continuous draft up 
the chimney ; this draft always removes air from the 
room, and fresh air is drawn in from outside to take 
its j)lace. Tlie air comes in through the cracks about 
the doors and windows, through the keyholes, and more 
or less tlirough cracks in the floors. The direction of 
the currents of air may be seen from Figure 40. When 
there are only one or two persons in a room, and the 
doors are opened frequently, sufficient fresh air is usually 
supplied from these sources. At night such ventilation 
is not enough. Unless the wind blows very hard, some 



RESPIRATION 



119 



arrangements should be made for constant change of air, 
such as opening a window at the top in such a way that 
those sleeping in the room will not feel a direct draft. 
An open fireplace, even if there be no fire in it, is an 
excellent means of ventilation, as shown in Figure 40. 

In houses heated by means of hot-air furnaces special 
devices are usually adopted for supplying fresh air. 




Fig. 40. — Ventilation. 
Showing the means by which air enters and leaves an ordinary room. 

The furnace is connected with what is called the cold 
box, which is open to the outdoor air. The air enters 
this box, passes into the furnace, is there heated, and 
then rises through the flues into the different rooms. 
All the while air is passing out of the rooms through 
cracks in the doors and windows, or rising through 
halls or ventilating flues in chimneys, which are usually 
left open in such houses. 

When houses are heated by steam radiators it is not 
so easy to keep the air pure; for although currents of 



120 PHYSIOLOGY AND HYGIENE 

air move up and down in the room they do not readily 
pass out, and we must depend for fresh air upon flues 
and open firef)laces. The difficulty in keeping a free 
circulation of air is partly the reason why a room 
heated by steam is apt to be "stuffy." In such a room 
there should always be some special arrangement for 
the outlet and inlet of air. Sufficient movement of the 
air may be obtained by means of open fireplaces, flues 
in the chimneys, ventilators around the windows, or 
windows slightly open at top and bottom. When a 
house with many doors and windows has many of its 
rooms opening into each other, ventilating flues are not 
especially necessary. 

When a room — such as a schoolroom or a public 
hall — holds a number of persons, special means should 
be adopted for replacing impure air. Such rooms are 
usually provided with special ventilating apparatus. 

It is worth while to remember, in any case, that cold, 
fresh air, from whatever source it may come, is less 
injurious than breathing repeatedly the air of a close, 
ill-ventilated room. There is one simple test of the 
ventilation of a room : Does the air seem fresh and 
sweet as you come from the pure outside air ? 

HOW TO RESTORE RESPIRATION 

Occasionally some accident stops a person's breath- 
ing and tends to produce suffocation. For example, 
when a person is submerged in water he can no 
longer take air into his lungs. If, however, the 
drowning person can be removed from the water 



RESPIRATION 



121 



while the heart still beats, and breathing can be started 
again, his life can usually be saved. After being taken 
from the water, the patient should be placed so that the 
head is lower than the shoulders, and turned face 
downward, to allow the water to run out of the mouth 
and throat. 

The process of arti- 
ficial breathing should 
then . be started. The 
patient should be placed 
on his back, with the 
head on a level with 
the body. The arms 
should be first pressed 
against the sides of the 
body, and then raised 
outward and upward 
until they meet above 
the patient's head. 
Lifting the arms in 
this way raises the Tig. 41. 
shoulders and ribs ; the 
size of the chest is 

thus increased, and air is drawn into the lungs. It 
is important to know that the air actually passes into 
the lungs. To be sure of this, the tongue must be 
drawn forward so as to open the throat and permit the 
air to pass. After the arms have been lifted, they 
should be lowered again, while a second person, if pos- 
sible, presses the abdomen and sides of the body. The 




The Method of moving 
THE Arms to produce Artificial 
Breathing. 



122 PHYSIOLOGY AND HYGIENE 

lowering of the arms and the pressure on the abdomen 
tend to force the air out by compressing the chest. 
The raising and lowering of the arms in this manner 
should be continued regularly from ten to twelve times 
a minute, and should be kept up until natural breatliing 
starts. Although this work is hard, it should be kept 
up for at least two hours if normal breathing is not 
resumed earlier. 

A feather or other light object placed in front of the 
mouth will show when natural breathing begins. If 
there is any motion of the feather to indicate natural 
breathing, the movements of the arms may be stopped. 
The person should then be wrapped in warm clothing 
or in blankets, and nature will complete the restoration, 
although it will be an aid to have the extremities of 
the patient rubbed during the whole process. This 
method of restoration should be employed if a person 
becomes nearly suffocated from any cause. Persons 
have sometimes been in the water a quarter of ail hour 
or even longer, and have still been brought back to 
consciousness. 

QUESTIONS 

1. What gas is necessary for oxidation? What products re- 
sult from oxidation ? 

2. Why should we keep our mouths shut except when talking 
or eating ? 

3. Where is the windpipe ? 

4. Of what use is the larynx ? 

5. Where are the lungs situated ? 

6. How does the blood get oxygen from the lungs? 

7. How is air drawn into the lunQ:s ? 



RESPIRATION 123 

8. Could a person breathe if there were a hole through the 
chest? Why? 

9. What form the walls of the chest? 

10. How is the chest cavity made larger or smaller? 

11. If air is taken into the chest only, why does the abdomen 
swell out with each inspiration ? 

12. How much of the air in the lungs is changed at a single 
breath ? 

13. How can we exercise the lungs ? 

14. What four things happen to the blood in the lungs? 

15. W^hat does the blood do with the oxygen it takes from the 
lungs ? 

16. If one should have too few red corpuscles in his blood, what 
would be the result ? 

17. What is respiration ? 

18. When you are running, can you breathe more easily 
through your mouth? If you do, can you run farther? 

19. Why does a schoolroom need better ventilation than a com- 
mon dwelling room? 

20. What are the purposes in ventilation ? 

21. What are the evils of indoor life? 

22. How^ should rooms heated by stoves and furnaces be venti- 
lated? 

23. What may be done to ventilate houses heated by steam ? 

24. How may natural breathing be restored w^hen a person has 
been almost drowned ? 



CHAPTER VI 

THE FRAMEWORK AND MOTION OF THE BODY 

The stomach digests food, the heart and the blood 
vessels are in constant action, the lungs never cease to 
expand and contract as long as we live. Those organs, 
then, all have a part in aiding us to accomplish the work 
that is given us to do. But with stomach, heart, and 
lungs alone we could neither step, nor speak, nor move 
in any way. We must have in addition muscles and 
bones. Of these our bodies are largely made, and it 
is to repair and renew these, as well as to render them 
of practical use, that we possess the organs about 
which we have already studied. 

THE SKELETON 

Most of the parts of our bodies are soft, and if there 
were not a hard framework to support them, we should 
be nearly as flexible as jellyfish. But inside the pli- 
able flesh we have solid bones, which serve, like the 
beams of a house, as a support for the softer parts. 
This framework of bones is called the skeleton. A 
grown person has in his body two hundred different 
bones. A child has even more, but several of the 
bones grow together later, making just two hundred. 

124 



FRAMEWORK AND MOTION OF THE BODY 125 



Clavicle 



HumefU9 



ffadius 




Tarsal Bones 
/ietalbrsalS 



Fig. 42. — The Human Skeleton. 



126 



PHYSIOLOGY A:N'D HYGIENE 



The bones are of different shapes and sizes. Figure 
42 shows the framework of the body, indicating the 
position and shape of the various bones. As will be 
seen from the figure, there is in the middle of the back 
a strong support, called the backbone. It is not one 
single piece, however, but a series of small bones 

fitting snugly to- 



U^^pino/ Cord 




gether and capable 
of being moved. If 
the back contained 
only one bone, it 
w^ould be stiff and 
easily broken, but 
this series of small 
bones enables us to 
bend the back with- 
out danger of break- 
^pim\ Cord ii^g it. Each of the 
smaller bones of the 
back is called a verte- 
bra. Figure 43 shows 
two vertebree. Many other animals liave backbones 
made up of vertebrae. These include fishes^ reptiles^ 
hirds^ and the four-footed animals with wliich Ave are 
familiar. All such animals are called vertebrates, ' 

Figure 42 shows a large, rounded box just above the 
backbone. This is the skull, wdiich forms the head. A 
side view is given in Figure 44. The skull is one of 
the most important parts of the body, because of the 
organs it contains. In it are the hrain^ the eyes^ the 
ears^ and the organs of taste and smelL 



Fig. 43. — Two Vertebr.^?: in Position. 

Showing the spinal cord passing 

throu2;h them. 



FRAMEWORK AND MOTION OF THE BODY 127 



The chest, as we already know, contains the heart 
and the lungs. It is nearly surrounded by curved 
bones called the ribs. These extend from the back- 
bone around to the front. Tlie heart and the lungs 



Cranium 



Facial} 
3ones ] 




Occipital 



Mandible 
Fig. 44. — The Human Skull. 

are surrounded and thoroughly protected by these ribs 
and the breastbone, or sternum. 

Each of the arms and legs is made up of several bones. 
In Figure 42 these bones are named. The bones of the 
arms and legs are the longest in the bod3^ Since they 
are the ones that must bear the heaviest strains, they 
are also the strongest bones of the body. 



128 



PHYSIOLOGY AND HYGIENE 



THE BONES 




Harrow 



Structure of Bone. — The different bones are of various 

shapes, but they are all so made as to have the greatest 

strength and at the same time to be comparatively liglit. 

For example, the long bones of the 

leg and the arm, which must bear the 

greatest strains, are hollow. Figure 

45 represents the longest bone of the 

leg, cut open lengthwise. At the 

ends the bones are spongy, but 

throughout the length of the shaft 

they are hollow. This shape gives 

the greatest possible amount of 

strength to the bone for a given 

weight of bony substance. Although 

not all the bones are hollow like those 

of the leg, still all are so built as to 

make the skeleton strong and light. 

This allows greater ease of motion 

than would be possible if the bones 

Fig. 45. — Xsection were heavier, and yet renders them 

OF THE Femur. sufficiently strong for the work they 

Showing the spongy ^^^g^ ^^^ 

ends and hollow 

(>gj^|.gj. Bone Materials. — Bones are made 

of two different materials, one of 

which is called mineral matter^ the other animal mat-- 

ter. The mineral matter is hard and brittle, and 

gives stiffness to the bone. If we put a bone upon 

a hot coal fire, and allow it to stay there for half 




FRAMEWORK AND MOTION OF THE BODY 129 

an hour, it will be very much changed. Though the 
shape will be the same, the heat has made the bone 
light and^very brittle, so that it can be crumbled to 
a powder in the fingers. The hot fire has burned the 
animal matter out of the bone, leaving only the mineral 
matter, which is something like stone, and cannot be 
burned. On the other hand, if we put a small bone, 
such as a chicken bone, into a dish of dilute nitric acid 
and allow it to remain there for a day or two, the acid 
will take out all the mineral matter. Upon removing 
the bone from the acid, we shall find it unchanged in 
shape and size, but soft and flexible, so that we can 
bend it, and perhaps even tie it into a knot. What 
is left is animal matter only. 

The mineral and the animal matter are united in bone 
so as to form one substance. The animal matter gives 
strength^ while the mineral matter gives hardness. 

Bones of Children. — Occasionally a child may fall 
down a flight of stairs with no ill effects save a few 
black-and-blue spots, while the same fall would be 
likely to injure a grown person seriously. The reason 
is that there is proportionately more animal matter in 
the bones of children than in those of adults, and the 
bones of children are therefore more easily bent and 
are not so brittle. In very early childhood the bones 
are made entirely of animal matter, and are conse- 
quently soft and flexible like the bone which has been 
soaked in acid. As the child grows, more and more 
of mineral matter is deposited in the bones, until finally 
they become hard and stiff. 



130 PHYSIOLOGY AND HYGIENE 

During the first few years of a cliild's life the bones 
are so flexible that they can be bent out of shape more 
easily than in later life. For this reason special pains 
should be taken to teach children to hold the body 
erect. A good carriage in walking can be learned by 
every one, but most easily by children. The chest 
should be held up properly, and the chin kept in, not 
thrust forward. If the chest is kept up and the 
shoulders are thrown back, the body will take the best 
position for walking and standing. When sitting we 
should take care to sit with head erect, and with the 
back against the back of the chair or bench. 

Misshapen Bones. — If the bones of a child are con- 
stantly bent in one direction, they will be deformed. 
Although it is easy for a child to stand and sit erect, it 
is equally easy to become ''round-shouldered." After 
the bones have hardened it is as difficult to change the 
habits as it was easy to form them, and later in life it 
may be impossible. Any kind of dress that causes 
strong and long-continued pressure on the bones is 
likely to cause a misshapen body. 

Wearing tight shoes Avill deform the bones of the 
feet. Figure 46 indicates the shape of the toes of a 




Fig. 46. — The Cramped Foot. Fig. 47. — The Uncramped Foot. 

person who wears tight shoes. Figure 47 indicates the 
shape the foot takes when it is not cramped. Wrongly 



FRAMEWORK AXD MOTION OF THE BODY 131 



shaped and tight shoes cause much discomfort and 
render walking difficult, besides putting the feet in 
such a condition that the person is likely to suffer from 
the effects all through life. Deformed feet may be 





Fig. 48. — An Improperly 
Shaped Shoe. 



Fig. 49. — A Properly Shaped 
Shoe. 



produced by shoes with narrow toes or with heels 
so placed as to throw the weight of the body upon the 
toes, as shown in Figure 48. A properly shaped shoe 
is shown in Figure 49. 

A habit even worse than pinching the feet is that 
of wearing tight bands round the waist, or tight cor- 
sets. This gives rise to serious deformities, affecting 
not only the bones but also the important vital organs 
of the abdomen Avhich are pressed out of proper posi- 
tion. The leather belts sometimes worn by boys and 
young m-cn with outing costumes, if drawn light 
around the waist, instead of being placed over the hips, 
are almost equally bad. Good health requires that 
the body be allowed to groAV as nature intended, 
unconfined by tight clothing. 



132 PHYSIOLOGY AND HYGIENE 

Habits of stooping over one's work, of leaning against 
a support instead of standing erect, of standing con- 
stantly upon one foot without bearing sufficient weight 
upon the other, of walking or sitting with stooped 
shoulders and with the head thrown forward, or of 
wearing clothing which binds the body — any of these 
habits will destroy the beauty of the form and impair 
bodily strength. Among the prime necessities for 
attractiveness in appearance is an erect manner of 
walking and sitting, without slouching. The cadets in 
the military schools owe much of their fine appearance 
to constant drills, which exercise all the muscles, and 
which keep the body erect. 

Repair of Broken Bones. — As many a boy knows 
from personal experience, bones will occasionally get 
broken in spite of the fact that they are tough and 
strong. Very fortunately, unlike broken teeth, bones 
w^hen broken can be mended. Each bone is supplied 
with one or more tiny blood vessels, Avhich furnish 
blood for its nourishment. The animal matter in the 
bone is alive^ and so is able to grow. 

If, after a bone is broken, the two ends are brought 
nicely together, this living part of the bone begins to 
make new bony material, which grows between the 
ends, finally uniting them again as strongly as ever. 
The bone must be kept still until it is firmly knit, for 
any motion w^ould pull the ends apart. For this rea- 
son the physician binds the broken bone tightly in 
splints. The setting of a hroheM hone consists simply 
in bringing the broken ends together and binding them 
in the proper position. 



FRAMEWORK AND MOTION OF THE BODY 133 



Since there is more animal matter in the bones of a 
child than in those of a grown person, broken bones 
are more easily mended in childhood. In old age the 
amount of animal matter is less, so that the bones are 
more brittle and more easily broken. They are also 
less easily repaired. 

CARTILAGE 

The framework of the body is not wholly bone. A 
part of it is made of a substance called cartilage. This 
is so soft that it can be cut with a knife. It is so 
flexible that it can be bent easily, but at the same time 
it is very tough. It is found in several places in the 
body where there is need of greater flexibility than 
bone would give. For example, the ribs are united 
with the breastbone at the front of the chest (see Fig. 
42) by little pieces of cartilage. This makes them 
slightly movable and not Cartilage 

easily broken. Little 
cushions of cartilage are 
also found between the 
vertebrae of the backbone, 
as indicated in Figure 50. 
Here they relieve the jar 
which would result from 
a jump, if the bones actu- 
ally touched each other. 
There are pieces of carti- 
lage around the larynx, and the outer ear is made 
entirely of cartilage covered w^ith skin. Cartilage 




Fig. 50. — Two Yertebr.i^. 

Showing the cartilage cushion that 

separates them. 



134 PHYSIOLOGY AND HYGIENE 

is not easily broken, but if once severed, it does not | 
mend so easily as bone. ■ 

JOINTS 

When we consider that the framework of our 
bodies is made of two hundred separate pieces, we 
wonder how they can ever be united in a firm struc- 
ture. They are fastened as firmly as the parts of a 
house are nailed together. In some places, as in the 
skull, they are so united that they cannot be moved. 
In other places, as at the elbow and in the fingers, they 
can be turned about freely. Whenever two bones come 
together they form a joint. If it were not for our 
joints we could not move ; and when an accident injures 
a joint, we become stiff and lame. There are two 
principal kinds of joints in the body, the hinge joint 
and the ball-and-socket joint. Let us see what each is 
like. 

A Hinge Joint. — The bones fbrming a hinge joint can 
be moved back and forth in one direction only, like a 
door on its hinges. The joints at the knee and the 
elbow are of this character, as is also each joint of the 
finger. If we try to move the finger or the elbow, we 
find that it will move in one direction only. The hinge 
joints are all so much alike that we need to study 
only one in detail. Let us take the knee joint as an 
illustration. 

Two bones come together at the knee to form the 
joint, — the thigh bone, or femur, and the shin bone, or 
tibia, as shown in Figure 51. The ends of these bones 



FRAMEWORK AND MOTION OF THE BODY 135 

are large and rounded, and the two fit together so 
as to be very easily moved. As can be seen from 
Figure 51, these bones are so shaped that they can be 
moved back and forth, but not sidewise. The ends 



Cartilage''^ 



Fibulan 




/Crc/c/a/ r:.,. 



Lotera/ 
Lig&meni 




Fig. 51. — The Bones forming the Knee Joint. 



of the bones, which are rounded and smooth in them- 
selves, are made still smoother by being covered with 
a layer of soft cartilage. 

To keep the parts of a bicycle in smooth running 
order we oil them. The various joints of the body 
are provided with a liquid that takes the place of oil 
in the wheel. This is the way it is arranged : the 
bones of the joint are partly surrounded by a thin 
membrane or tissue, which supplies a liquid to the joint 
between the two bones. The liquid moistens the ends 
of the bones, thus preventing friction. If it wore not 
for this liquid the bones would rub against eacli other, 
and it would be impossible to use the joint. The 



136 



PHYSIOLOGY AND HYGIENE 



shapes of the bones themselves and their smooth ends, 
together with the liquid, allow very free motion. 

How the Bones are held together. — No matter how 
nicely two bones might be fitted together, if they were 
not well fastened in some way the slightest twist would 
put them ''out of joint." As it is, a bone occasionally 

Anterior 
Liffament 



Patellai 





Capsular 

Posterior 
LigdmeDt%rib}\ 

Fig. 52. — The Knee Joint. 
Showing the ligaments connecting the bones. 

slips out of place, but only when there is a severe 
strain of the joint. To avoid such danger the ends of 
the bones are fastened together by two kinds of con- 
necting bands which extend from one bone to the other. 
These are ligaments and muscles. 

The ligaments are made of a white, tough, flexible sub- 
stance. Several ligaments may be seen in Figures 51 
and 52. They pass from one bone to the other across 
the joint. Some of them are placed in front, some at 
the sides, and some at the back. The ligaments are, 
however, rather loose, so that while the bones cannot 
slip out of place, they might, if they were held in no 
other way, move too freely. 



FRAMEWORK AND MOTION OF THE BODY 137 

In addition to the ligaments, therefore, the bones 
are held in position by means of certain muscles. The 
motion of the bones at the knee joint is produced by the 
muscles, all of which lie above the knee. From the 
ends of the muscles, long, slender cords or tendons pass 
down over the knee joint and are attached to the bones 
below the knee. These muscles are elastic and, being 
slightly stretched, they help to hold the bones in close 
contact. Outside of the muscles is the shin^ which 
covers the bones, tendons, ligaments, and muscles, form- 
ing a protection for them all. 

We move our joints so unconsciously, as we take a 
step forward or sit down in a chair, that we hardly 
realize how complicated they really are. But when we 
consider that so complicated and well-fitted an arrange- 
ment is provided simply to enable us to move a knee, 
we cannot fail to hold these bodies of ours in great 
respect. A single hinge joint means that we have 
two smooth bones rounded just so as to fit into each 
otller, strong ligaments to bind them together, muscles 
and tendons to assist in movement, and a protecting 
skin surrounding all. 

Other Hinge Joints. — The other hinge joints of the 
body are like the knee joint. In all cases the bones 
are rounded and are moistened Avith the liquid to pre- 
vent friction. All are held together by muscles and 
ligaments, and all are so arranged that they can be 
moved in only one direction. The joints at the elbows, 
at the wrist and ankle, and in the fingers and leg are 
all hinge joints. 



138 



PHYSIOLOGY AND HYGIENE 



A Ball-and-Socket Joint. — To show the arrangement 
of a ball-and-socket joint we Avill study the shoulder joint. 
In general such a joint allows the bones to move in e very- 
direction. We can lift the arm above the head, to the 
front, to the side, turn it around, and bend it backward 
as far as the hinge joint at the elbow will allow. The 
two bones which form the shoulder joint are the 

shoulder blade, or scapula, 
and the upper arm bone, 
or humerus. The shapes 
of these bones may be seen 
from Figure 63. 

As is evident from the 
illustration, the shoulder 
blade has a somewhat 
rounded hollow. The up- 
per end of the arm bone 
is rounded like a ball 
and fits into this socket or 
hollow. Since the end of 
the arm bone is a ball, and the socket in the shoulder 
blade is a hollow cavity, the arm can be moved in all 
directions. It is this shape of the bones that gives us 
our great freedom in lifting the arms. The ends of the 
bones are not only rounded, but they are made particu- 
larly smooth by being covered with cartilage, and they 
are also moistened with liquid like that in the hinge 
joint. 

The bones are bound together at the shoulder by just 
such strong bands as we saw at the knee. There is, 




EiG. 53. — The Bones of the 
Shoulder Joint. 



FRAMEWORK AND MOTIOX OF THE BODY 139 




Ccp5ular 



Fig. 54. — The Shoulder Joint. 

Showing ligaments. 



however, as Figure 54 shows, only one important liga- 
ment. It is a loose, leathery sac fastened to the shoulder 
blade. From the shoulder 
blade it passes over the 
joint on all sides, and is 
attached to the upper end 
of the arm bone, so as to 
cover the joint com- 
pletely, and hold the end 
of the arm bone in the 
socket. If this ligament 
should be cut, the bones 
could be taken apart very 
easily. 

The strength of the shoulder joint is due very largely 
to the fact that it is surrounded by strong muscles. 
These muscles cover the joint on all sides, giving it 
great strength and firmness. The muscles in the 
shoulder have tendons which pass down over the joint 
and are fastened to the arm bone, thus holding it 
firmly in position. 

Other Ball-and-Socket Joints. — The only large ball- 
and-socket joints in the body, besides those at tlie 
shoulders, are at the hips. The hip joint allows the leg 
to be moved in various directions, but the movement is 
not quite so free as that at the shoulder. 

Injuries to Joints. — There are two kinds of injuries 
to joints which are connnon. They are dislocations and 
sprains. 

A bone pulled out of its place in the soc^ket pro- 



140 PHYSIOLOGY AND HYGIENE 

duces a dislocation. If, for example, a fall or a wrench 
should pull the end of the arm bone from the hollow 
in the shoulder blade into Avhich it fits, Ave say the 
shoulder is dislocated. When a bone is thus wrenched 
from its proper position it cannot be moved in the 
ordinary way. The bone must be put back in its 
normal place in the joint. This should be done by a 
physician, unless it chances to be one of the small 
bones in the finger, which almost any one can pull back 
into place by slightly pulling the bones apart and then 
slipping the dislocated bone into position. When a bone 
is dislocated, it is very likely that some of the connect- 
ing bands or ligaments may be strained or slightly torn. 
A sprain is a tear or strain in one or more of the 
ligaments of a joint. A sprain is common in con- 
nection with dislocated joints, but it occurs frequently, 
also, when there is no dislocation. A violent strain at 
any joint may cause such a pulling on the ligaments as 
to injure them and produce a sprain. The injury is 
sometimes very slight and sometimes very great. A 
sprain may be even more serious than a dislocation or a 
broken bone, requiring a longer time to heal. In case 
of a sprain, the joint should be placed in a comfortable 
position. Water, as hot as can be endured, should 
then be applied, and this should be followed by cold 
water. The joint should be bound tightly with band- 
ages. It is wise, of course, to rest the joint, but it is 
not wise to keep it perfectly still during the healing 
process, lest it be stiff for a long time. The sprain 
will be more quickly healed if, beginning say a day or 



FRAMEWORK AND MOTION OF THE BODY 141 



two after the accident, the joint is used a little each 
day. 

THE MUSCLES 

A large part of the food we eat is used to enable us 
to move. The motions of the body are brought about 
by the muscles. The lean part of meat consists of 
muscles, and the muscles in our bodies are very similar 
in appearance to lean beef, as it comes from the market. 
The joints, ligaments, and tendons of themselves would 
be unable to move the body. It is through the muscles 
that the power is applied. 

Structure of a Muscle. — To understand the structure 
of a muscle, let us look at the one in the front part of 
the upper arm, known 
as the biceps, which we 
see represented in Fig- 
iiire 55. The biceps 
muscle, as the figure 
shows, is a rather long 
mass of flesh, large in 
the middle but taper- 
ing at the two ends. 
The middle part is 
made up of reddish 
flesh, and is the mus- 
cle itself. At the ends 
firm, white bands or cords, which neither contract nor 
expand, connect the muscle w^ith the bones. These 
are tendons or cords. 




Ufno 
Fig. 55. 
Showing the method of attachment of 
the biceps muscle to move the fore- 
arm. 



142 



PHYSIOLOGY AXD HYGIENE 



All the muscles in the body are connected with bones 

by such tendons. The tendons differ in length, some 

of them being very short. A series of such cords at 

the wrist extends from the arm to the fingers, and at 

the ankle from the leg to the toes. 

If we grasp the left arm just below 

the elbow with the right hand, and 

then open and close the fingers of the 

left hand, we can feel the motion 

of the arm muscles. These muscles 

move the fingers, and are connected 

with them by the long tendons which 

pass to the finger bones. If we clinch 

the fingers of the left hand and grasp 

the wrist with the right hand, we can 

feel how tightly the tendons are 

stretched as they pass along the front 

of the wrist. Figure 56 shows their 

arrangement. 

A muscle seems to be a solid mass 

Fig. 56. ^^ flesh. If wc examine it under a 

Showing the muscles microscope, however, we find that it is 

andtendonsof the peg^^y made up of an immense number 
arm. 

of threads or muscle fibers, as they are 
called. We can see how the fibers are arranged, from 
Figures 57 and 58. These muscle fibers are too small 
to be seen without a microscope. They run lengthwise 
in the muscle, and they are very numerous. They are 
bound together by a thin, delicate substance which 
fastens them firmly to one another. 



FRAMEWORK AND MOTION OF THE BODY 143 



Great numbers of minute blood vessels run in and 
out among the fibers, furnishing the muscle with its 
nourishment, as shown in Figure 36, facing page 108. 
These blood vessels are the capillaries which, as we 
learned, receive the blood when it leaves the arteries, 
before its return to the heart by way of the veins. The 
walls of the capillaries are so thin that the food which is 




Fig. 67. — A Bit of Muscle. 
Slightly magnified. 



Muscle' 
Fibers 

Fig. 58. — A Bit of Muscle. 

Highly magnified, showing muscle 

fibers. 



in the blood passes through them to the muscle libers, 
giving them power to move and building tliem up. 

Involuntary Muscles. — There is another kind of 
muscle which we hear less about. These muscles are 
called involuntary muscles, because we do not consciously 
control them. The most important are those which form 
the walls of the stomach and intestines and propel the 
food, and those wliich contract and expand tlie arteries 



144 PHYSIOLOGY AND HYGIENE 

and thus regulate the flow of blood. These muscles are 
very different in appearance from the ones we have 
just described, but they also are made of microscopic 
fibers, bound together in flat masses. They are much 
more sluggish in their action than the other muscles, 
and we not only have no control over them, but we 
are not even conscious of their action. But since they 
drive the food along the intestines and control the flow 
of blood, they are of great importance. 

The Contraction of a Muscle. — If we stretch a rubber 
band, it becomes longer and thinner ; when we let go 
of the ends, it shortens and becomes as thick as before. 
In somewhat the same way the muscles of the body 
are shortened, the muscle growing thicker as it con- 
tracts. If we clinch the left fist, grasp the left arm 
above the elbow with the right hand, and then lift 
the forearm forcibly, Ave find that the biceps mus- 
cle becomes larger and harder as the hand is raised. 
After the arm has been lifted, the muscle may hold it 
up for a time, but to do so constant effort is required. 
The moment we relax the effort the arm falls of its 
own weight. To lift the arm the muscle must be con- 
tracted, but no muscular effort is required to lower it. 

There is, however, on the back of the arm, as shown 
in Figure 55, a muscle which acts in the opposite way 
from the biceps. If this muscle shortens or contracts, 
it pulls the arm down, stretching the biceps, as may be 
understood from Figure 55. The two muscles thus 
form a pair opposed to each other ; when one of them 
contracts, the other is lengthened. One lifts the arm 



FRAMEWORK AND MOTION OF THE BODY 145 

up, and the other straightens it. It is the contraction 
of a muscle that produces motion or action. 

What makes the Muscles contract. — In addition to 
the blood vessels in each muscle, there is connected 
with it a white cord — a nerve. This nerve is larger in 
the large muscles than in the small ones. The nerve 
is made up of nerve fibers^ and each muscle fiber re- 
ceives its nerve fiber. All of these fibers are connected 
with the spinal cord, and through the spinal cord, with 
the brain. 

Why are the muscles connected with the brain? Just 
this : The nerves serve much the same purpose as 
electric wires. The muscles never contract of their 
own accord any more than an electric bell will ring 
itself. To ring the bell we must press a button. This 
sends an electric current through the wire and causes 
the bell to ring. In about the same way the muscles 
of the body act, when the proper kind of message 
comes to them. If the current, or stimulus, as it is 
called, never comes, the muscle will remain quiet for- 
ever. The stimulus is given to the muscle through 
the nerves. The brain, which is the central station 
for all kinds of action, is able to send stimuli down 
to the muscles through these thousands of little threads, 
and when the muscles get the message they contract. 
The involuntary muscles are excited into action in 
tlie same way, for, although we do not will to move 
them, the brain sends stimuli to them as it does to the 
other (voluntary) muscles. 

This power which the brain has over the muscles 



146 PHYSIOLOGY AND HYGIENE 

is very wonderful. Not only can the brain cause 
a single muscle to contract at any time, but it can 
cause many muscles to act together, either in connec- 
tion with one another or separately. For example, when 
a boy throws a stone, he lifts his arm, closes his fingers 
about the stone, presses one foot hard against the 
ground, and sets his body firmly to assist in the throw- 
ing ; then he must quickly contract the muscles of the 
arm and shoulder, and loosen the stone from his fingers. 
In all, from fifty to a hundred muscles must be con- 
tracted at nearly the same time. 

The boy does not realize that he is using such a 
wonderful machine, or even that he is contracting 
muscles. He simply thinks, ''I will throw the stone," 
and the brain gives the proper order to the numerous 
muscles. The message must be sent to each of these 
muscles at the same time, and must cause each to 
contract just the right amount. If the brain should 
make a mistake, and cause some muscles to contract 
too much or not enough, the stone would go wide of 
the mark. This really happens many times when the 
boy is learning to throw straight. We say that " prac- 
tice makes perfect"; that is, the boy must learn how 
to throw the stone just where he wants it to go. In 
other words, the brain must learn how to make the 
muscles work in the proper way. 

Number and Positions of the Muscles. — The fleshy 
part of our bodies is made up of a little more than 
two hundred muscles. They differ in size and shape. 
Most of them are fastened to at least two bones, so 



FRAMEWORK AND MOTION OF THE BODY 147 



that as the muscles are contracted the bones are moved. 
Figures 56 and 59 show how the muscles are arranged 
in the body, though compara- 
tively few are represented 
here. The various muscles 
are so attached to the bones 
that they can be moved in 
all the directions that the 
joints permit. We can bend 
the arm or straighten it ; we 
can move it to either side or 
turn it around, each motion 
being produced by a different 
set of muscles. 

Muscle Growth. — It is a 
peculiarity of muscles that 
the more they are used, the 
stronger they grow. Tlie 
blacksmith, because he con- 
stantly swings his heavy 
hammer, develops very strong 
muscles in his arms. When 
a person learns to ride a 
bicycle, he finds that certain 
muscles of his legs are weak, 
but, as he continues the exer- 
cise, the muscles become 
stronger, until he can climb 
even high hills without any great strain. One set of 
muscles, however, should not be developed and others 




."LES OF THE Body. 



148 PHYSIOLOGY AXD HYGIENE 

neglected . The man who has all his muscles moderately 
well developed is stronger and more healthy than the 
one who has highly developed his arm muscles with- 
out exercising equally the other muscles of the body. 

If muscles are not used, they become small and 
weak. If a muscle were left idle for a few months, it 
would lose much of its power, so that we could not use 
it at all. Children in their active play ordinarily use 
all their muscles, so that they develop evenly. But 
as people grow older, certain muscles are used less and 
less. We take the trolley-car and the elevator to save 
the trouble of walking : as a result, we find that we 
cannot walk so far as we could a few years ago. We use 
the right hand in our work rather than the left, and 
the left hand is weaker and less skillful. We sit in a 
comfortable easy-chair until the muscles of the back are 
weakened, and as a result we cannot sit upright for 
any length of time without fatigue. Although we really 
want our bodies to be well developed and vigorous, we 
get into these habits of neglecting the muscles from 
carelessness. 

Exercise. — It is worth our while to make special 
efforts to use all the muscles of the body. If we find 
that certain muscles are weak, those are the ones that 
we should take pains to exercise. Too frequently we 
do the reverse. If we find something that is particularly 
hard for us to do, perhaps sweeping or sawing wood, 
that is just Avhat we should do every day, until the 
muscles are so developed that we find it easy work. 

In large cities the chances that young people have 



FRAMEWORK AND MOTION OF THE BODY 149 

for muscular exercises are limited. For this reason 
gymnasiums have been erected in cities, and especially 
in schools and colleges. The person who commonly 
needs the most urgent advice to take exercise is the 
boy or girl who is ambitious to become a scholar. 
He prefers to spend all his time at his books, and is 
not willing to give even a little time each day to ac- 
tive exercise. He should remember that the person 
who studies all the time is likely to be outstripped 
by the one who studies and plays as well. Many 
students break down because they do not take sufficient 
exercise. 

Out-of-door games afford the best possible exercise, 
since these not only develop the muscles but give the 
player fresh air and recreation at the same time. Such 
games as baseball, golf, and tennis are excellent. Bicy- 
cling is good exercise, though '' century runs " and very 
fast riding are dangerous, and the habit of bending 
over the handle bars makes one liable to what is known 
as bicyclers' stoop. Brisk walking and running are 
very good exercise ; strolling can hardly be called exer- 
cise at all, although in other ways a quiet walk in the 
open country is beneficial. 

The royal maxim for perfect body development is : 
A perfect body requires the development of all muscles; 
all powers unused are iveakened. 

Stimulants. — Some people have the mistaken idea 
that they can increase their muscular power by the use 
of what are called stimulants, generally meaning by this 
some form of alcoholic drink. For a short time after a 



150 PHYSIOLOGY AND HYGIENE 

person has taken the alcohol there may be a slight 
increase of mnscular power, but a decrease of such 
power follows very soon, so that there is no real gain. 
If alcohol is used in any considerable amounts, there is 
a great weakening of muscular power. 

The use of alcohol will unfit any boy for good work 
in an athletic contest. Under no conditions does al- 
cohol used as a stimulant enable an athlete to do his 
best. It has a tendency both to weaken the muscles 
and to dull the senses. Boys and j^oung men some- 
times make the mistake of trying to " brace themselves 
up" for a contest by the use of alcohol. Professional 
athletes know enough to let alcohol alone under these 
circumstances. 

QUESTIONS 

1. Of what is the framework of the body made? What is 
this framework called? 

2. AVhat organs are inclosed in the skull ? 

3. How are the long bones of the arm and leg constructed ? 

4. Of what are bones made? 

5. If we did not have enough lime in our food, what effect 
would it have on the bones? 

6. How do children's bones differ from those of a grown 
person? 

7. What happens to the bones if there is unnatural pressure 
upon them ? 

8. W^hat are the results of wearing tight clothing? 

9. How are broken bones repaired ? 

10. What is cartilage? Where is it found? 

11. What two kinds of joints are there in the body? 

12. How is a hinge joint made ? # 



FRAMEWORK AND MOTION OF THE BODY 151 

13. Mention all of the kinds of supporting and connecting tis- 
sues found in the body. 

14. What is a ligament ? 

15. Wliat is a tendon? 

16. How does the ball-and-socket joint differ from the hinge 
joint ? 

17. How are the bones in a ball-and-socket joint fitted and 
fastened together ? 

18. Why do we have a hinge joint at the knee instead of a ball- 
and-socket joint? 

19. Why do we need a ball-and-socket joint at the shoulder? 

20. What is meant by dislocation ? 

21. What is a sprain? 

22. What are the parts of a muscle ? 

23. How is a muscle contracted? 

24. How is the muscle contraction controlled by the brain ? 

25. W^hy is it that a person falls over if he suddenly faints or 
dies, when in a sitting or standing position? 

26. What effect have exercise and lack of exercise upon the 
muscles ? 

27. What are the best kinds of exercise ? 

28. Give some examples from your own observation of loss of 
power from disuse. 

29. What is the effect of alcohol upon the muscles ? 



152 



PHYSIOLOGY AND HYGIENE 



A LIST OF THE CHIEF BONES IN THE BODY 



(► All forming the skull. 



1 



Forming the 
thorax. 



The nasal bones. 
The frontal bones. 
The parietal bones. 
The occipital bone. 
The mandible or lower jaw. 
The sternum or breastbone. 
The ribs from the backbone to the sternum. 
The vertebrae forming the spine. 

The sacrum at the lower end of the vertebrse between the hips. 
The coccyx, a small piece of bone below the sacrum. 
The scapula or shoulder blade. 
The clavicle or collar bone. 
The humerus, from the shoulder to the elbow. 
The radius and the ulna, from the elbow to 
the wrist. 

The carpals or wrist bones, eight in number. 

The metacarpals, from the wrist to the fingers. 

The phalanges or finger bones. 

The ilium. 

The pubis. . 

The ischium. J ° 

The femur, from hip to knee. 1 

The tibia and fibula, from knee to ankle. | 

The tarsals or ankle bones. ^ The leg. 

The metatarsals, from ankle to the toes. 

The phalanges, or bones of the toes. 



1 



The arm. 



Fused together to form the hip bone, or pelvic 



CHAPTER VII 

THE KIDNEYS AND THE SKIN AND THEIR 

DUTIES 

WASTE PRODUCTS 

Use of Food by Muscles. ~ A muscle is like a little 
steam engine which cannot work except when burning 
fuel. We have seen how the different foods are carried 
throughout the body by the blood. When these foods 
reach the capillaries, the muscle fibers take what they 
need for their use. The proteids serve especially to 
make new muscle tissue, which is constantly needed 
to take the place of that used up by the work of the 
muscle. The proteid or building foods are also needed 
to repair any injury that may have come to the muscle, 
and to supply the new material needed when the 
muscle is developing and growing. The sugars and 
fat^ with some of the proteids^ simply furnish heat and 
force ; in other words, they are fuel foods. The food 
is oxidized in the muscles by means of the oxygen 
brought by the blood. As a result, force is developed 
to enable the muscles to contract, and heat is produced 
to warm the body. 

Waste Products of Muscle Action. — When coal or 
other fuel is burned, or oxidized, smoke and gas pass 
off into the air and ashes are left in the grate. These 

153 



154 PHYSIOLOGY AND HYGIENE 

are ivaste products^ because they are not used and can- 
not be used for heating. When the fuel food of the 
body is oxidized in the muscles and tissues, waste 
products are left, which are of no further use. These 
are carbon dioxide, water, and other substances. 
These waste products must be gotten rid of. We 
have already seen how the carbon dioxide is taken 
away by the blood, and breathed out of the body from 
the lungs. We know also that some water goes out 
in the breath. A larger quantity of water passes off 
through the skin and from tlie kidneys, as we shall 
see presently. The third waste product, known as 
urea, is taken from the blood by the kidneys, and 
finally leaves the body in the urine. 

A large proportion of the food we eat is taken by the 
muscles to supply muscular force. Some of it is used 
in the brain, a small amount in the glands, and certain 
quantities in everj^ active part of the body. But, al- 
though the uses made of the food may differ in the 
various places, the same oxidation takes place, and the 
same waste products always result. 

Secretions and Excretions. — The materials produced 
by the body are generally classified under two heads. 
Those like carbon dioxide and urea are simply Avaste 
products and of no use at all. They are generally 
called excretions. But some of the materials are pro- 
duced for special purposes. For example, the gastric 
glands in the stomach produce gastric juice to aid 
digestion, and the salivary glands produce saliva for the 
same purpose. Materials which are thus of use to the 



KIDNEYS AND SKIN" AND THEIR DUTIES 155 



body are called secretions, and they are generally pro- 
duced by special organs called glands. We have 
already learned of several of these, the salivary glands^ 
the gastric glands^ and the pancreas. 

The excretions are not only of no use, but if alloAved 
to collect in the body they act as poisons. Hence they 
must be gotten rid of promptly. Some of them can 
pass off through the lungs in the breath, and some from 
the skin in perspiration, but some are disposed of in 
other ways. The urea in particular is eliminated by 
special organs. 

THE KIDNEYS 

Urea is thrown off from the body by means of a pair 
of organs called the kidneys. Each kidney is, in a grown 




E ic. . GO . — T 1 1 1-: K 1 1 ) X k y s. 
The one on the right is cnt open to show the tubes which secrete the 

urea. 



156 PHYSIOLOGY AND HYGIEXE 

person, some four inches long and one and a half inches 
wide. The kidnej^s are located in the back part of the 
abdomen, just below and behind the stomach, and close 
to the backbone. Their shape is indicated in Figure 60. 
A large artery brings the blood to each kidney, as the 
same figure shows, and a large vein takes the blood 
away. There is also a tube, called the ureter, that 
passes from the kidney to the bladder, and takes away 
the material removed from the blood by the kidney. 

The kidney is made up of a large number of blood 
vessels, together with a series of small tubes, called 
kidney tubules, as shown in Figure 60. As the blood 
passes through the kidney, the tubules take the urea 
and some other solid matters which are dissolved in 
the blood. This material, together with considerable 
w^ater, which is also taken from the blood, is poured 
into the ureters, and passes to the bladder and then out 
of the body. 

. THE SKIN 

Although mainly of use as a covering for the body, 
the skin has special duties of its own. It serves as a 
means for the passing out of waste and for regulating 
the heat of the body. A healthy skin is absolutely 
necessary if the body is to be in good condition. Slug- 
gishness or improper action of the skin in its work is 
likely to cause sickness. 

Structure of the Skin. — The skin is a thick sheet like 
a close-fitting garment, covering the entire body. A 
grown person has about sixteen square feet of skin. 



KIDNEYS AND SKIN AND THEIR DUTIES 157 



\Epidermis 



}Dermis 



The average thickness is about one sixteenth of an 
inch, though it is thinner in some places than others. 
It is thickest on the soles of the feet and the palms of 
the hands. 

If we take a thin 
slice of skin and 
look at it through 
a microscope, we 
find that it has two 
layers, one outside 
of the other, as 
shown in Figure 61. 
The outer layer is 
called the epidermis, 
and the inner layer . 
is the dermis. We 
can stick a pin 
through the epider- 
mis without feeling 
it, but the instant 
the point enters the 
dermis we feel pain. 
All the epidermis, 
except a thin layer 
on the inner side, is practically lifeless, and contains 
neither nerves nor blood vessels. The dermis is full 
of blood vessels and nerves, and is very sensitive. 

The Epidermis. — The epidermis, tliough lifeless at 
the outer surface, is continually growing on the inside, 
where it is in contact with the dermis. Verv often 




, zFat 
Y Cells 



\,Sweat 
Oland 



Fig. 61. 



■A Section of a Bit of Skix. 
Highly magnified. 



158 PHYSIOLOGY AND HYGIENE 

Avlien we look at our hands we can see one or more bits 
of loose skin which may be pulled off without harm. 
The outside skin is all the time being thus w^orn or 
rubbed off, bit by bit, and it keeps growing from the 
inside. The epidermis is so firmly attached to the 
dermis tliat the two are not easily separated. Occasion- 
ally w^e burn a spot on the finger, or are severely sun- 
burned, so that blisters appear, that is, a little watery 
material has gathered between the epidermis and the 
dermis. If the blister is broken and the outer skin 
removed, the dermis is exposed. This is always sen- 
sitive and tender. 

Thick Parts of the Epidermis. — A boy who is an en- 
thusiastic ball-player is very proud of certain bunches on 
the palms of his hands, called callosities. The constant 
rubbing and striking of the ball causes the epidermis 
to grow more rapidly at these spots than elsewhere, and 
so it becomes thicker. Any part of the skin that has 
an extra amount of use grows thicker than the rest, this 
being nature's means of protection against injury. 

If we wear tight or poorly fitting shoes that con- 
stantly rub the toes, round bunches called corns are 
formed by the thickening of the skin. We can pre- 
vent the growth of corns by wearing shoes large 
enough not to pinch the toes, and yet snug enough 
not to chafe the feet. It is difficult to get rid of corns 
after they have once formed, so it is wise to avoid 
the great discomfort which they cause by taking proper 
care of tlie feet. Children who go barefooted in tlie 
summer rarely have either corns or deformed toes. 



KIDNEYS AND SKIN AND THEIR DUTIES 159 



Occasionally certain parts of the skin groAv too thick, 
causing what are known as warts. Children are apt to 
be superstitious about these growths, because they come 
and go so suddenly. Some children believe that warts 
result from handling toads, and that they can be cured 
by the use of certain charms, both of which are absurd 
ideas. If a wart otows 

large enough to be ^*..=^ ir-nuir 

really troublesome, it 
can be burned off with 
acid, but under ordi- 
nary conditions warts 
had better be let alone. 
They will disappear 
without assistance in 
time. 

Hair. — Nearly all 
parts of the skin are 
covered with hair, 
which is an outgrowth 
from the epidermis. 
Figure 62 shows that ^ 
each hair extends down ^I^OWIOS Cdls ^ 

through the skin into a 

Showing its root and follicle. 
little pocket. This is 

called the hair follicle. A very small mound, or 

papilla, which is the place where the liair grows, is 

located at the bottom of the pocket. The hair is thus 

constantly growing at its root, and being tlius pushed 

out of the pocket. In other words, the hair grows from 




Uoif 
Gland 
'hair 
Fol/fde 



Hair Papilla 



160 PHYSIOLOGY AND HYGIENE 

the roots, not from the ends. If a hair is pulled out, 
the little mound at the root usually keeps on sending 
out more substance, so that a new hair grows to take 
the place of the old one. If the whole follicle, includ- 
ing the mound at the bottom, is destroyed, no new hair 
will grow. 

Each hair is supplied with oil from tiny oil glands. 
These open into the follicle from the sides, as shown in 
Figure 62. They produce an oily substance that mois- 
tens the outside of the hair, keeping it soft and flexible. 
If the hair is brushed frequently, the oil will be distrib- 
uted over it, so that no hair oil need be used to keep it 
in good condition. We should never brush the hair 
with anything but a soft hairbrush. Wire brushes are 
likely to scrape the scalp so that the follicles may be 
injured, and they may pull out the hair. 

Hair is lifeless and has no sensations. If we place a 
hand upon the head, we may feel the touch, but the 
feeling is not in the hair itself; we feel the pushing of 
the hair against the nerves in the skin. We say that a 
cat's whiskers are very sensitive. The feeling is not in 
the hairs themselves, but in the very delicate nerves 
about the roots. 

Hair grows on all parts of the body excepting the 
palms of the hands and the soles of the feet. In some 
places it hardly more than reaches the surface and is 
therefore so short that Ave do not notice it. Certain 
animals, like the cat and the dog, have very thick 
hair, which serves as a protection and covering for 
the skin. The hair of human beings is of no particular 



KIDNEYS AND SKIN AND THEIR DUTIES 161 



use except for ornament and for its protection to the 
head. 

The hair of the head has a tendency to fall out and 
produce baldness. This is especially true of the hair 
of men. Just why this is the case physicians do not 
know. Some think that it is due largely to the habit 
of wearing heavy hats with stiff rims Avhich bind the 
scalp ; they advise the use of loose, cool hats. Others 
are of the opinion that "shampooing" the hair with 
the aid of diluted ammonia and soap, or other sub- 
stances, causes baldness. It is necessary, however, to 
keep the hair clean, and it may safely be washed with 
water containing a little soap. The soap should be 
carefully rinsed off and the hair thoroughly dried. 
Hair oil and hair restorers of all kinds should be 
avoided. 

Toe Nails and Finger Nails. — The toe nails and finger 
nails are parts of the epidermis developed in a special 
way. Figure 63 represents 

a cross section of a finger, ^opl 

showing the nail. The 
purpose of the nails is to 
protect the fingers and 
toes. They also help to 
beautify the hand, and 
they aid us in picking up 
small objects by enabling 
us to grasp them firmly. 

The nail grows outward from the root at the base, 
and unless the root is injured, the growth continues as 




Fig. 03. —A Sectiox thkoigh 

THE Tir OF THE FiNGEK. 

Showiiiij: the nail. 



162 PHYSIOLOGY AND HYGIENE 

long as we live. The wliite '' half moon " at the lower 
edge is where the nail is new and quite thin. If a nail 
is injured, it sometimes comes off. A new one will 
grow in its place, unless the root has been destroyed. 
We all dislike finger nails that are grimy or dirty at the 
ends. They should be kept clean and neatly trimmed 
with a knife or scissors. They sliould be cut only at 
the ends ; neither the surface of the nail nor the skin 
covering the root should be scraped or cut. 

Some young people form the habit of biting the 
nails. This is likely to injure the shape of the fingers, 
besides rendering the person disagreeable to all with 
whom he comes in contact. While various reminders 
may be employed to aid in overcoming the habit, such 
as some bitter substance placed upon the nails, the 
difficulty should be conquered by the exercise of Avill 
power. 

The Dermis. — The dermis, shown in Figure 61, is 
thicker tlian the epidermis, and is very different in 
structure. It consists principally of a mass of fibers, 
running in every direction. The fibers are packed 
close together on the side next to the epidermis, but 
they are less dense near the muscles, Avhich lie below 
the skin. Tiny fat cells are found between the fibers, 
as shown in Figure 61. The dermis is full of blood 
vessels, so that, when cut, it always bleeds. It is also 
very sensitive, because of the many nerves it contains. 
Some of these nerves are particularly sensitive to heat 
and cold. 



KIDNEYS AND SKIN AND TPIEIR DUTIES 168 



FUNCTIONS OF THE SKIN 

As a Protection. — The epidermis is made of flat, 
scalelike cells, packed together so closely that they are 
a very great protection to the flesh beneath. Some 
of the^tells may be seen in Figure 61. We can plunge 
the hand into poisons without injury, because the sub- 
stances cannot quickly make their way through these 
cells. Some diseases, as we shall see later, are caused 
by microscopic living germs getting into the body and 
growing there. The epidermis helps to protect us 
from such diseases by keeping out the germs. If they 
get through the skin, they may produce sores, boils, 
abscesses, or even more serious troubles. They cannot 
pass through the healthy epidermis, but often a slight 
scratch or bruise breaks the skin enough to let the 
germs in. As a result of the growth of these germs, 
the scratch becomes inflamed and painful, or perhaps 
develops a sore or boil. If the germs can be kept out, 
these sores will not appear. Special care should be 
taken to ivasli all cuts and bruises^ and to cover them 
with a plaster or bandage so as to prevent bacteria from 
entering where the epidermis has been broken. 

As an Excreting Organ. — AVhen we luive been taking 
vigorous exercise, or on a very warm day, small drops 
of moisture, or sweat, appear on the forehead, the nose, 
and other parts of the body. This moisture is secrLM:ed 
by the stveat glands^ of which we liave about two and 
a half millions in our skin. 



164 



PHYSIOLOGY AND HYGIENE 



A sweat gland is too small to be seen with the naked 
eye, but it consists of a tube passing through the epi- 
dermis, and coiled up in a knot on the inside, as shown in 
Figure 61. This tube secretes the sweat, which passes 
out through a minute hole in the epidermis, called a 
pore, and is discharged upon the surface of the skin. 
The skin of the whole body is covered with these tiny 




Fig. 64. — A Bit of Skin as it appears under a Microscope. 
Showing furrows and pores. 

pores, each leading into a gland. Though they are 
found all over the body, there are more of them upon 
the forehead, the palms of the hands, and the soles of 
the feet than elsewhere. If we look at the skin of the 
fingers, we see that it is covered with irregular furrows. 
If we compare two fingers, we find that the furrows are 
unlike. The pores in the skin of the fingers are along 
the ridges between these furrows, as shown in Figure 
64 ; they may be seen with a magnifying glass. 



KIDNEYS AND SKIN AND TIIErR DUTIES 165 

We notice the sweat only when it appears in drops 
upon the surface of the skin, or when it moistens tlie 
clothing. It is then being poured out of the glands in 
especially large quantities, but the glands are bringing 
it out all the time. The sweat is usually evaporated 
as fast as it comes to the surface, not becoming visible, 
but simply moistening the skin. If we hold the fingers 
close to a cold window pane, vapor collects on the glass. 
This shows that water is evaporating from the fingers, 
even though sweating is not apparent. 

The sweat itself is principally w^ater, though small 
amounts of salt and other substances are dissolved in 
it. In fever, sweating is reduced very much or stops 
entirely. 

As a Regulator of Body Temperature. — The air, both 
in doors and out, is usually cooler than our skin. The 
air is constantly taking heat from the skin, cooling it 
and the blood which flows near the surface. The 
faster the blood flows through the skin, the faster it 
is thus cooled by the air. 

We have already seen that the skin is full of small 
blood vessels. These, like all the rest of the blood 
vessels, can be expandccd and contracted as is needed. 
If the body is producing more heat than usual, the 
brain causes the blood vessels in the skin to expand : 
the blood then flows faster, and more blood is cooled. 
If the body is not producing as much heat as usual, 
these blood vessels are made to contract. The blood 
is thus kept aAvay from the surface and does not lose 
its heat by giving it out to the air. By opening and 



166 PHYSIOLOGY AND HYGIENE 

closing these blood vessels, the brain is able, Avithout 
our knowledge, to increase or decrease the amount of 
heat lost through the skin. In this way our tempera- 
ture is controlled very closely and accurately. If the 
body is too warm, the blood vessels expand and let the 
heat out ; if too cold, they contract and keep it in. 

The nerves that are sensitive to heat and cold are 
located in the skin. When the warm blood pours 
through the skin, it warms these nerves and we feel the 
heat. When the blood vessels contract, so that the 
warm blood is kept away from the skin, these nerves 
are cooled by the air outside, and we feel cold. On a 
warm day we feel hot, not because the body is warmer 
than usual, but because the warm blood is flowing 
over the heat nerves in the skin. The body has practi- 
cally no sensations of heat and cold except those in the 
skin and in the lining of the mouth and the digestive 
canal. 

Cold-blooded Animals. — Frogs, snakes, and certain 
other small creatures are called cold-blooded animals. 
The amount of heat produced in their bodies is not 
very great, and it passes off as fast as it is formed. 
The cold-blooded animals are never much warmer than 
the air about them. On a warm day they may be very 
warm, on a cold dciy they will be cold. Such animals 
are usually rather sluggish, especially in cold weather. 

Warm-blooded Animals. — The amount of heat pro- 
duced in our own bodies, and in those of such animals 
as dogs, cats, and horses, is comparatively large. This 
heat warms the blood to a certain temperature, wdiich 



KIDNEYS AND SKIN AND THEIR DUTIES 167 

does not change with the temperature of the air, but 
remains about the same all through life. We call ani- 
mals whose bodies keep the same temperature warm- 
hlooded. Their blood is usually warmer than the air, 
although on a hot summer's day the air may be the 
warmer. 

To keep the blood at this temperature requires con- 
siderable activity and a large amount of food, just as 
a considerable quantity of coal is required to keep our 
rooms very warm in winter. A cold-blooded turtle 
may live for six months without eating a mouthful ; 
its activity is so slight that the small amount of food 
stored in the body is enough to sustain life, and no 
heat is needed to warm the body. A warm-blooded 
animal, on the other hand, must not only have a large 
supply of food, but it must have this food more or less 
regularly, and it can live but a short time if deprived 
of the regular supply. 

When we are in perfect pliysical condition, the tem- 
perature of our bodies is almost exactly 98^"^ F. If the 
temperature rises above this point or falls below, it is 
commonly an indication of ill health. We feel so much 
warmer on a hot summer afternoon than we do on a 
winter morning that it seems to us the temperature of 
our bodies cannot be tlie same, but a test with a ther- 
mometer would show, in botli cases, just the 98.1°, if we 
are well. 

Some warm-blooded animals — bears, for example — 
sleep throughout the winter. When thus aslee[^ they 
burn less fuel (food) and do not keep warm ; their body 



168 PHYSIOLOGY A:N^D HYGIENE 

temperature falls very much, but this does them no 
injury. When they wake in the spring, they begin to 
burn food more rapidly and are soon warmed again. 
Such animals are called hibernating animals. 

Regulation of Heat by the Lungs. — The skin is aided 
in regulating lieat by the lungs. As our bodies are 
always producing much more heat than is needed to 
warm them, a large proportion of this heat must be given 
out, in order to keep the proper temperature. Much of 
the extra heat passes off in breathing. If we take in a 
breath of cool air and then breathe it out close to the 
back of the hand, we find that it is much Avarmer. 
The warm blood passing through the lungs has heated 
the air, and the blood is correspondingly cooled. The 
amount of heat which the body loses in breathing differs 
very greatly on different days. In winter the cold air 
may take much heat from the blood in the lungs. 

Sweating as a Means of regulating Heat. — In summer 
the air may be about as warm as the body, and in 
this case no heat at all would be lost through either 
tlie lungs or the skin by simply warming the air. In 
hot weather, therefore, another means of getting rid of 
the extra heat is provided. If we wet a finger and 
blow upon it gently, or hold it in the wind, the finger 
feels cool. The water is evaporated by the wind, 
and it takes a large amount of heat to evaporate water. 
The heat required to evaporate the water on the finger 
is taken from the finger itself, leaving this somewhat 
cooled. In the same way the sweat that is poured out 
upon the skin is evaporated, taking heat from the body 



KIDNEYS AND SKIN AND TPIEIR DUTIES 169 

and leaving this correspondingly cooler. The more we 
perspire the more the evaporation of the sweat cools our 
bodies. 

The sweat glands are connected with the brain 
through nerves, and when the body has too much heat 
a message from the brain makes the glands begin to 
secrete sweat profuselj^ The sweat is rapidly evapo- 
rated, and in this way we get rid of the extra heat that 
would make tlie blood too hot, if there were no way of 
escape. The evaporation of the sweat takes so much 
heat that the body is kept at its ordinary temperature, 
no matter how warm the day may be. 

Dogs do not sweat very much, and are apt to suffer 
greatly from the heat of summer. By their rapid 
breathing, or panting^ they take in large quantities of 
air, which, passing through the lungs and taking heat 
from the blood, helps to keep down the temperature of 
the body. 

** Taking Cold.'' — There are people who seem to take 
a certain pride in their sensitiveness to drafts, and who 
are always ready, and expecting, to ''take cold." Such 
persons usually do take cold oftener than other people, 
because they wrap their necks closely when out of 
doors, and in the house they sit near a register or witli 
shawls about the shoulders if the air of the room is a 
bit cliilly. 

Now ''taking cold" is a liabit Avhich may be almost 
wholly avoided, if we will learn to treat the skin properly. 
In tlie first place, colds are not due to exposure to cold. 
Explorers do not take cold when in the Arctic regions, 



170 PHYSIOLOGY AND HYGIENE 

although they may do so after their return home. 
Soldiers can sleep on the damp ground or may be 
out in the rain for days at a time without catching 
cold. People who live out of doors seldom suffer from 
colds. We may feel cold from such exposure, but we 
do not take cold. We know from experience that we 
can have the face and the hands exposed when the tem- 
perature is very low, without catching cold. 

Yet it is true that we do sometimes suffer this 
disagreeable malady if cold air strikes some part of 
the skin which is usually protected. A slightly cool 
draft striking the bare shoulders may be sufficient 
cause. This fact has given rise to the idea that the 
best way to prevent taking cold is to protect the 
neck and shoulders by means of extra wraps. This 
is a wrong method. If we should cover our faces with 
wraps in the same way, they would soon become so ten- 
der that drafts striking them would produce colds. If, 
on the other hand, we should expose the neck as we do 
the face, it would soon become so accustomed to changes 
in temperature that it would be as impervious to cold 
as is the face. It is, then, very unwise to get into the 
habit of wearing furs or mufflers around the neck, or of 
turning up the coat collar about the ears. The extra 
protection may be necessary for comfort on an occa- 
sional extremely cold day, but the more we wrap the 
neck the more sensitive it becomes, and consequently 
the more liable we are to take cold. 



KIDNEYS AND SKIN AND THEIR DUTIES 171 



QUESTIONS 

1. What are the three waste products of muscle action ? 

2. What becomes of each of these waste products ? 

3. What are excretions and secretions? Is sweat a secretion 
or an excretion? 

4. W^hat organs produce secretions? 

5. Mention as many kinds of secretions as you can. 

6. What is the duty of the kidneys? 

7. How are the kidneys constructed ? 

8. What are the two parts of the skin ? 

9. Where is the epidermis, and what are its characteristics? 

10. What are callosities and corns? Can callosities and blisters 
both be produced by rubbing? How? 

11. What are the parts of a hair? 

12. How should we take care of the hair ? 

13. What are warts? 

14. How do the toe and finger nails grow ? Have the nails any 
sensations ? 

15. What is the structure of the dermis ? 

16. How does the skin act as a protection ? 

17. What are the sweat glands? 

18. How is the heat lost through the skin? 

19. What are cold-blooded animals? 

20. If a cold-blooded and a warm-blooded animal were placed in 
an ice box, what effect would be produced on each ? 

21. How is the heat of the body regulated by the lungs? 

22. Why do we need sweating to aid iu regulating body heat? 

23. How may we avoid taking cold? 



CHAPTER VIII 

THE CARE OF THE SKIN 

The skin, as we have learned, is an organ of great 
importance to the body. It is important as a protect- 
ing organ, as an organ of excretion removing waste 
products from the body, and it is at the same time the 
chief organ concerned in regulating the temperature. 

BATHING 

Cleanliness. — In order that the skin may keep in 
healthy condition, it is necessary that the sweat glands 
be kept free and open. The fat glands connected with 
the hairs constantly pour oil upon the skin, and the 
sweat glands secrete considerable solid material with 
the sweat. These substances remain upon the skin, 
and unless they are frequently removed they will in 
time clog the pores, and will also give to a person an 
unpleasant odor which renders him disagreeable to 
those about him. Frequent bathing and washing of 
the body is therefore desirable. No positive rule can 
be given as to the frequency with which we should 
bathe. A daily bath is advisable, although it is not 
essential to health. 

Cold Baths. — Cleanliness is not the only reason for 
bathing. The bath stimulates the skin, and this would 

172 



THE CARE OF THE SKIX 173 

render it of value even if it were not required for pur- 
poses of cleanliness. We have seen how the delicate 
blood vessels expand and contract with changes in tem- 
perature. The muscle fibers of these blood vessels and 
the nerves controlling them need exercise as much as 
do the other muscles of the body. Our habits of life 
give them little chance for this needed exercise ; we 
keep our rooms uniformly warmed, and when we go 
out of doors on a cold day we cover all parts of the 
body except the face. Under these conditions the 
blood vessels in the skin are likely to become sluggish, 
and they need stimulation. The simplest way of giv- 
ing this is by means of the cold bath. 

Effects of a Cold Bath on the Skin. — A cold bath, 
Avhether a plunge in cold water, a shower bath, or merely 
a sponge bath, has always with a vigorous person the 
same effect. At first there is a sensation of cold, which 
causes the blood vessels to contract. For a short time 
the skin may be white and cold, but this is presently 
followed by what is called the reaction. The blood 
vessels open once more, allowing the warm blood from 
the interior to flow rapidly through the skin. The 
skin becomes flushed and warm, and there is a feeling 
of exhilaration, due to this after glow. 

A person should leave the water while still under 
the influence of the reaction. If he stays longer, he 
becomes chilly again, and will remain cold and uncom- 
fortable for hours. The length of time the after glow 
lasts depends upon the person, the temperature, and 
the water. It remains longer Avith salt water than 



174 PHYSIOLOGY AND HYGIENE 

with fresh. The greater the after glow, the more bene- 
ficial is the bath. If the body is rubbed vigorously 
with a rough towel after the bath, the glow is much 
increased, and the benefit correspondingly greater. 
Indeed, vigorous friction Avith a towel is of fully as 
much benefit as the bath itself. 

The expansion and contraction of the blood vessels 
thus brought about furnishes the skin with the needed 
exercise. If a person lives out of doors, exposed to all 
sorts of weather, such exercise is not necessary ; but to 
people spending most of the time in the house, such 
a bath is to the skin w^hat the gymnasium is to the 
muscles. A warm bath does not accomplish tlie same 
purpose. It frequently makes one tired instead of 
exhilarated, and should therefore be taken only after 
the work of the day is done, instead of in the morning. 

Sometimes women and young girls who have not a 
great amount of vitality find that the cold plunge, or 
even the cold sponge bath, fails to give -the desired 
reaction. In such a case the body should be accus- 
tomed to the cold water gradually. Little by little 
the space covered by the cold Avater may be extended 
until the skin has become sufficiently toughened so 
that the bath may be made general. This may usually 
be accomplished in the course of half a dozen mornings. 
To become accustomed to the cold plunge it is best to 
begin with slightly warm Avater, using it a little cooler 
each day, until Ave find Ave can endure Avater which is 
really cold. All young persons will find in the cold 
bath, either plunge or sponge, a source of pleasure 



THE CARP] OF THE SKIN 175 

which, after they have become accustomed to it, the 
warm bath cannot give. 

Cold Baths a Protection against Colds. — This skin 
exercise renders the cold bath a protection against 
colds. If we will accustom ourselves to a cold sponge 
bath every morning, and will avoid covering the neck 
with thick wraps, we are much more likely to escape 
the habit of taking cold. The person who, by means of 
heavy wraps, protects his skin from exposure, and who 
takes only warm baths, is pretty sure to get into a con- 
dition that favors taking cold. He then regrets that 
he "takes cold so easily." The remedy may be in his 
own hands. It consists in adopting a mode of life that 
will give his skin the needed exercise. 

Hot Baths. — We can easily test the difference in 
effect of the cold and the hot bath. If we bare the 
arm and pour cold water upon it, then rub it briskly, 
the skin becomes red and warm with the after glow. 
If we plunge the arm into water as hot as can comfort- 
ably be borne it first grows red, then turns Avhite, and 
there is no after glow. There are times, however, when 
a hot bath is beneficial. It may enable one who is rest- 
less and wakeful to go to sleep, since it draAVS tlie 
blood from the brain. When we feel a cold coming 
on, a hot bath or even soaking the feet in hot water 
may draw the blood from the throat and nose suffi- 
ciently to prevent the cold from developing. An occa- 
sional hot bath is also desirable for the cleansing of the 
body, even though cold baths are frequently taken. 



176 PHYSIOLOGY AND HYGIENE 

CLOTHING 

We should remember that we wear clothing for the 
purpose of comfort or adornment rather than to protect 
us from taking cold. For comfort it is necessary, in 
cold weather, to cover the body very completely with 
clothing. We should remember, however, that the 
clothing does not warm the body, but simply holds in 
our body heat, keeping it from passing off by way of 
the skin. Any clothing that conducts or sends oif heat 
rapidly will cool the body quickly. Clothing that con- 
ducts heat slowly will keep the body warm. Linen and 
cotton carry the heat away rapidly, while woolen cloth- 
ing holds it back. We should therefore wear linen or 
cotton garments in the summer time, and woolen cloth- 
ing in the winter. Coarsely woven cloth, which is filled 
with air spaces, carries the heat away very slowly. 
Clothing made of such material is, then, the very best 
for keeping the body warm in cold weather. Similarly, 
two light garments, worn one over the other, are warmer 
than one heavy one of equal weight. The air space 
between the two acts as a "non-conductor" of heat. 

When we sleep, our bodies should be more warmly 
covered than when we are awake. A good rule to keep 
in mind is that for sleeping the feet should be warmi 
and the head cool. As the body, during sleep, needs 
rest as much as possible, it ought not to be compelled to 
keep up any extra amount of heat. Paper is a material 
which readily holds back heat, and if a couple of news- 
papers be placed between two pieces of bed clothing 



THE CARE OF THE SKm 177 

they do as good service in keeping the body warm as 
a blanket. 

BURNS 

Burns are very common injuries to the skin and are 
often very serious. In case of a slight burn we can 
usually relieve the pain for a time with cold water. 
One of the best applications for a burn is a paste which 
can be quickly made by rubbing soda or hahing powder 
into some vaseline or sweet oil. Place this paste, which 
should be thin enough to spread easily, on a clean cloth 
and apply it so that it shall completely cover the burn. 
Another method is to apply a cloth wet in a solution of 
baking powder or saleratus and water. This solution 
is, however, less soothing than the paste, and the cloth 
must be soaked in it frequently. The burn should 
always be protected from the air. This may be done 
in an emergency by applying linseed oil,, lime ivater,, or 
eveii flour^ to the place, but no cotton wadding should 
be put on the wound or anything else that might leave 
little particles on the surface. If the burn is neither 
very deep nor very extensive, it will heal readily; but 
if it is severe, it should be cared for by a physician. 

Life might sometimes be saved if people would re- 
member what to do in case the clothing catches fire. 
If the clothing gets afire, one should catch up any 
woolen article that may be at hand, wrap it closely 
around the burning clothing, and immediately lie down 
flat upon the floor or the ground, and roll over and over. 
Without air the iire cannot burn, and the rapid rolling, 



178 PHYSIOLOGY AXD HYGIENE 

even if one cannot reach any woolen stuff to serve as an 
extinguisher, will usually put out the fire. People 
have lost their lives by standing up while attempting 
to remove burning clothes. The flames rise, and if 
the person is standing, he is very liable to breathe the 
Are into his lungs. This causes almost instant death. 
If a person whose clothing is on fire loses his wits 
and starts to run, he should be thrown down as a means 
of saving his life, for running is very dangerous. He 
should then be wrapped in a rug, a blanket, a coat, or 
any similar heavy article that may be at hand, to 
smother the flames. After the fire is out, if the flesh 
of the person is burned, the clothing must be removed. 
Care must be taken, however, that the skin is not torn 
off. The clothing is likely to stick to the skin, and if 
it does so, it should be allowed to remain, at least where 
it adheres, the cloth being cut off around the place if 
necessary. If there are blisters, they should be opened 
and the liquid pressed out. Any further treatment 
should be given by a physician. 

FROSTBITES 

The freezing of fingers, toes, nose, or ears is not an 
uncommon occurrence on an extremely cold day. In 
such a case, the water in the blood and the muscles is 
actually turned to ice. If the frozen parts are thawed 
out slowly, no permanent injury may result ; but if 
they are thawed rapidly, serious trouble may follow, 
which may render amputation of the toes or fingers 
necessary. For this reason frostbites should be thawed 



THE CARE OF THE SKIN 179 

slowly. Rubbing the frozen parts with snow or cold 
water is recommended. This will thaw them out with 
the least possible danger of injury. In general, to 
preserve a part of the body that has been frozen, it 
must be promptly but very gradually thawed. After the 
thawing has been completed, the person may be warmed 
and given hot coffee or some other warm drink. 

Many people wrongly suppose that the uncomfort- 
able affection of the feet known as " chilblains " is the 
result of frostbite. They are really due to getting 
the feet very cold and then warming them too quickly, 
and do not appear in children with a vigorous circu- 
lation. Warming cold feet over a register or in a 
stove oven is very likely to cause the diificulty. The 
best way to protect the feet against chilblains is to wear 
warm stockings and thick shoes in cold weather, and 
give the feet plenty of exercise. 

QUESTIONS 

1. Why should the sweat glands be kept free and open? 

2. What is the use of sweat? 

3. What is the effect of the cold bath ? 

4. What are the advantages of the cold bath ? 

5. How do cold baths act as a protection against colds ? 

6. What is the difference in effect between the cold and the 
hot bath? 

7. What clothing is most suitable for summer? For winter? 

8. Are silk underclothing and stockings as useful as avooIcu? 
Why? 

9. Why should the body be warmly covered during sleep ? 

10. What should be done when a person's clothing catches fire ? 

11. What should be done for frostbite ? 



CHAPTER IX 
STIMULANTS AND NARCOTICS 

Many people have the habit of using certain sub- 
stances which interfere with the health of various parts 
of the body. These substances are of two general 
classes, known as narcotics and stimulants. 

By a stimulant we generally mean a drug which, on 
being taken into the body, excites an unusual activity. 
A substance may be a stimulant, even though it is a 
poison. Strychnine, for example, though a violent 
poison, may in small quantities act on the body as a 
stimulant, exciting it so excessively that a slight breath 
of air may throw the person into convulsions. 

Narcotics have just the opposite effect. They soothe 
and dull the actions of the body, and have a tendency 
to put people to sleep. Although narcotics and stimu- 
lants seem thus to be very different, no sharp line can 
be drawn between them. The same drug may produce 
both effects, its first effect being that of a stimulant, 
while its later and more lasting effect is that of a nar- 
cotic. When such a substance, alcohol for example, 
is taken in a small amount, it seems at first to pro- 
duce a stimulating effect, but it also produces a nar- 
cotic effect which may not at first be noticed. When 
a larger quantity is taken, the narcotic effect is un- 
mistakable. 

180 



STIMULANTS AND NARCOTICS 181 

OPIUM 

Opium is one of the most dangerous of narcotics. 
Morphine and laudanum are two common forms of the 
drug. Paregoric and soothing sirup^ both of which 
contain opium, are especially dangerous, and should 
not be given to children. Opium dulls the senses and 
finally puts a person to sleep. The reason why it 
is so dangerous is that it has a tendency to produce 
a terrible craving for opium, 

A person begins by taking a small amount, possibly 
prescribed for him by a physician as a remedy for 
toothache, headache, or neuralgia. The drug not only 
soothes the pain, but produces a pleasant, restful feel- 
ing. Whenever the person has a pain which he wishes 
to relieve, he uses the same remedy, or he even imagines 
the pain for the sake of taking the drug. Soon the 
small doses with which he began cease to produce the 
desired effect, and he takes larger amounts. Before 
he suspects the fact, he has become an " opium eater," 
and no longer even pretends to make the excuse that 
he takes the drug as a medicine. 

Opium destroys the ability to think clearly and ruins 
the moral nature. The opium eater frequently becomes 
a liar and a thief. His health is undermined. He no 
longer finds pleasure in work or in recreation, and after 
a while even the dviicr itself ceases to oive him relief or 
satisfaction. The use of the drug so affects his Avill 
power that when he finds himself a slave to the habit 
he has not the strength of will to restrain the appetite. 



182 PHYSIOLOGY AND HYGIENE 

When once the terrible habit has obtained a hold upon 
a man, it is almost impossible for him to control it. 
The use of opium in any form, except under the direct 
advice of a phj^sician, is consequently exceedingly 
dangerous. Many physicians are unwilling to pre- 
scribe it, knowing as they do how easily the habit is 
formed. 

The use of chloral and cocaine is equally dangerous, 
the effects being similar to those of opium. 

TOBACCO 

Tobacco is a milder narcotic than opium, and one 
much more widely used. Tobacco contains a poison 
which is deadly when taken in considerable quantity. 
It is a question whether the amount of this poison 
taken into the body by a grown person who smokes 
but little is enough to produce injury. There can be 
no question about the ill effects of tobacco on young 
people, however moderately it may be used. Used 
freely, it is undoubtedly injurious to adults. 

Moreover, mild narcotics like tobacco share with the 
stronger narcotics, though in less degree, that power of 
making the user want more and more of them. There 
are many other excellent reasons for refraining from 
the habit of using tobacco. 

1. Tobacco is of absolutely no value to the healthy 
body. It neither acts as a food nor does it serve any 
other useful purpose. 

2. The use of tobacco by young people may cheek the 



STIMULANTS AND NARCOTICS 183 

proper growth and development of the body. CJareful 
study of college students has shown that those who are 
addicted to the use of tobacco are, on the average, con- 
siderably less developed than those who let it alone. 
The tobacco habit handicaps a boy in his physical 
development at the very start of life. 

3. The use of tobacco temporarily reduces one's 
muscular power. 

4. Its excessive use by young people often causes 
heart trouble. The '^ cigarette heart " is well known 
to physicians. Brain difficulty, insanity, and even 
death are sometimes traceable to tobacco. 

5. It is an expensive habit. The money spent for 
tobacco could certainly be put to better use, and could 
be employed in ways that, to a young person at least, 
would give more pleasure and profit. 

6. It is a habit that renders one disagreeable to 
others and tends to selfishness. Most people who do 
not use tobacco, women especially, find the use of it 
by their acquaintances very disagreeable. Its use 
sometimes tends to selfishness and to a disregard of 
the feelings of others. 

7. The use of tobacco is likely to lead boys into inju- 
rious co7)ipany^ inviting them to idleness and to other 
bad habits. 

Of all forms of tobacco, cigarettes probably do the 
greatest amount of injury. A person who uses cig- 
arettes is likely to ''inhale" the smoke. This means 
breathing the smoke into the lungs, which is far more 
injurious than simply taking it into the mouth. Boys 



184 PHYSIOLOGY AND HY^GIP^NE 

in particular should know this, for cigarettes are gener- 
ally used by them on account of their cheapness. 

For these reasons the wise course is to leave tobacco 
alone. 

ALCOHOL 

« 

One of the greatest dangers that a young person 
has to meet is that of acquiring the alcohol habit. 
Fortunately, it is not so common as the tobacco habit. 
Nevertheless, it has destroyed the lives of hundreds of 
thousands of young people, and has been a stumbling 
block in the way of hundreds of thousands of others. 
It has led to countless crimes, and has caused an ines- 
timable amount of poverty and suffering. The use of 
alcohol is particularly dangerous, because it frequently 
obtains a mastery over young people without their real- 
izing the fact. 

The Use of Alcohol in Excess. — The effect of alcohol 
upon the body depends largely upon the amount used. 
When speaking of the use of alcohol in excess, people 
usually mean its use in quantities sufficient to produce 
intoxication, or with a frequency that keeps the person 
more or less under its influence. The use of alcohol 
in such quantities is disastrous to health. It injures 
the action of the heart, interferes with circulation, 
and impairs the digestive powers. Moreover, it has a 
very important influence upon the moral nature. The 
drunkard loses his sense of responsibility and ceases 
to be a normal man. His whole body becomes dis- 
eased and unable to carry on its proper functions. His 



STIMULANTS AXD NARCOTICS 185 

mind becomes dull and his ambitions disappear. The 
use of alcohol in large quantities destroys a man's 
chance of the highest success. Alcohol causes the 
death of thousands of men and women every year. 

Use of Alcohol in Smaller Quantities. — When alco- 
holic drinks are used in quantities insufficient to pro- 
duce intoxication, their effect upon the body may also 
be serious, although not always apparent. The injury 
is so gradual that there may be little to call attention to 
it. Some people use wines or beers in small amounts for 
years without being apparently injured by them. Never- 
theless, alcoholic drinks, when habitually used, even in 
small quantities, frequently produce decidedly injurious 
effects. They are never needed by persons in health, 
and they are certainly dangerous to all young people. 

The effect of using alcohol in small quantities does 
not appear at once. Its action when so used was 
shown recently by a series of experiments upon dogs, 
made by Dr. Hodge, of Clark University. Four 
dogs were selected from the same litter, all as nearly 
alike as possible. Two of them were given only ordi- 
nary food. The other two were treated in exactly the 
same way, except that they were given a small amount 
of alcohol with each meal. They were never given 
alcohol enough to make them intoxicated, and, taking 
into consideration the relative size of the dogs and 
a man, the amount given Avas relatively abinit as 
much as would be taken by many moderate drinkers. 
At first the four dogs were practically alike, but little 
by little differences began to appear between those that 



186 PHYSIOLOGY AND HYGIENE 

were given the alcohol and those that had nothing but 
the regular food. 

In the course of a few months the "alcohol" dogs were 
quite inferior in appearance to the other two. By the 
end of a year and a half the difference was very marked. 
The ''alcohol" dogs were sleepy, and had a general ap- 
pearance of worthlessness. They were less active than 
the other dogs, and were much more quickly tired out. 
They would not bring back a ball when it was thrown 
for them so often as the others, and they frequently 
lay down to rest. In other words, the use of alcohol 
had lowered the intelligence, the brightness, and the 
muscular power of the dogs. 

If a moderate use of alcohol affects dogs so much 
in eighteen months, we may be sure that it has some 
injurious effect on the people who continue its use in 
this way for years. Whatever success in life has been 
made by a man who is a moderate drinker, he would 
certainly have amounted to as much without the alco- 
hol, and perhaps a great deal more. 

Competition is so great in these days, in business, in 
the professions, and, in fact, along every possible line of 
work, that the boy or young man of the present day 
needs to have every possible power of mind and body 
at his command. The man with clear and unimpaired 
brain, with a healthy, well-cared-for body, with body 
and brain controlled by a determined, resolute Avill — 
he is the man who will make a success in the coming 
years of the twentieth century. 

The Alcohol Appetite. — We have already learned that 



STIMULANTS AND NARCOTICS 187 

one of the most dangerous things about alcohol is its 
tendency to create a desire for more. This desire may 
be very slight at first, but it is likely to grow. More- 
over, although at first a small amount of alcohol is all 
that a person wants, or can drink, when his body be- 
comes accustomed to this amount, he almost without 
knowing it takes a little more. Quite unconscious of 
how serious a thing it is, he slowly increases the amount 
used, sometimes by taking a larger amount of weak 
liquors and sometimes by taking stronger ones. He 
begins with beer and finally uses distilled liquors. The 
appetite grows with indulgence, and sooner or later 
it may become so firmly fixed that he is quite unable 
to break it. 

Danger of the Appetite. — The fact that the appetite 
grows slowly and imperceptibly is what makes alcohol 
so dangerous. If a boy or young man could appreciate 
how the appetite is increasing, if he could realize to 
what it is likely to lead him, and if he could under- 
stand at the beginning how he is slowly becoming bound 
by a habit, he would in most cases curb the habit before 
it developed much strength. But the habit grows im- 
perceptibly, and at the same time undermines his will. 
until it finally produces disastrous results. 

The continued use of alcohol, moreover, is likely to 
crush out all desire to reform. The alcohol appetite 
might be overcome in most cases if the person had a 
sufficiently strong desire to do so ; but his will power 
and his desire for a better life are taken a\\ay as the 
appetite grows upon him. 



188 PHYSIOLOGY AXD HYGIENE 

While it is true that some people use alcohol in small 
amounts without becoming mastered by the habit and 
without developing an alcohol appetite, it is equally 
true that with thousands of others the small amount of 
alcohol that is taken at first leads to tlie development 
of an appetite. It is never safe for a boy to run the 
danger of developing such an appetite. He may not 
become mastered by it, but experience has shown that 
in many cases the boy finds himself in time mastered 
by the habit. It is never possible to predict what will 
be the result. Drunkards are commonly made out of 
boys and girls who do not intend to use enough 
alcohol to injure them. If a boy never begins to use 
alcoholic liquors, he will never become a drunkard; 
but if he does begin, even in a mild way, he places 
himself among those from whom drunkards are made. 
The only sure way to avoid this danger is to avoid its 
beginning, and, in avoiding that, the boy also insures 
for himself a healthier body, a clearer brain, and a 
better chance for success in life. 

QUESTIONS 

1 . What is the difference between a stimulant and a narcotic ? 

2. Wliat is the effect of opium, and why is it a dangerous 
drug ? 

3. Why should tobacco not be used ? 

4. What is the effect upon the body of using alcohol in excess ? 

5. What are the probable effects of a moderate use of alcohol ? 

6. What do you regard as the strongest reason for avoiding 
alcoholic drinks ? 



CHAPTER X 
THE NERVOUS SYSTEM 

Every large factory must have a superintendent. 
Otherwise the persons employed to do various tasks 
would work independently of one another, and as a 
result little would be accomplished. The superin- 
tendent is indeed the most important man in the 
entire factory. 

Within our bodies various actions are going on. 
Over two hundred muscles, numerous glands, and many 
other organs are constantly at work. If they should 
act independently there would be great confusion. In 
our bodies, however, as in the factory, there is a super- 
intendent, whose duty it is to control all the different 
parts and keep them working in harmony with each 
other. A few of the body actions, like the beating of 
the heart, can take place without direct connnand from 
the superintendent, but with the others the order of 
the superintendent is required before the organs will 
work at all. 

The muscles will never act unless they are com- 
manded to do so by the central controlling organ. As 
we have already learned, the organ that corresponds 
in the body to the superintendent of a factory, and 
that controls the numerous activities, is the brain. 

189 



190 



PHYSIOLOGY AND HYGIENE 



The brain is connected with eveiy part of the body 
by a series of nerves. This is the organ with which 
we think, and by means of which we will to do any- 
thing. The brain also causes a great many actions to 
take place in our bodies without any knowledge on 
our part. AVe do not realize, for instance, that the 
brain is constantly sending messages to the blood ves- 
sels of the skin, causing them to open or shut. 

THE BRAIN 

The brain fills the bony box called the skall. Figure 
65 shows its shape and structure. It is a very large 




'Brtathing 

/aso Motor 

Heart Control 

\3waHomhj 



Fig. 65. — The Human Brain. 



organ, that of an adult weighing some three pounds. 
There is considerable difference in the weight of vari- 
ous brains. The more intelligent races commonly have 
large brains, while those of less intelligence usually 



THE NERVOUS SYSTEM 191 

have smaller ones. There are, however, among individ- 
uals, some remarkable exceptions to this general rule. 
The brain, as we may readily believe from its w^onderf ul 
powers, is a very complicated organ. It is divided 
into three main parts, as may be seen from Figure 65. 

The Medulla Oblongata. — Forming the very lowest 
part of the brain is the medulla, or medulla oblongata, 
which lies between the spinal cord and the main part 
of the brain. It is very small, not more than one and 
a quarter inches in length, and yet it controls some of 
our most important body actions. As Figure 65 indi- 
cates, the hreathing^ the vasomotor system (i.e, expan- 
sion and contraction of blood vessels), the heart control^ 
and swallowing^ together with other functions, are the 
special care of the medulla. 

The Cerebellum. — A little higher than the medulla 
is situated a larger rounded part of the brain, about 
half as large as a baseball, called the cerebellum. It 
is somewhat flattened and, as Figure 65 indicates, is 
marked with numerous furrows. It lies over the 
medulla. The cerebellum is thought to influence mus- 
cular action. We have seen how wonderfully the 
muscles are adjusted so as to act together, as, for 
instance, when a boy throws a stone. This is sup- 
posed to be accomplished in part through < the action 
of the cerebellum. 

The Cerebrum. — The cerebrum is the largest part of 
the brain. Figure 65 shows that it is covered with 
deep furrows which divide it into folds called convo- 
lutions. These folds are not exactlv alike in all brains, 



192 



PHYSIOLOGY AND HYGIENE 



though the larger ones are almost always present. The 
cerebrum is divided by a very deep furrow into two 

parts, called the right and the 
left hemisjjTieres, The division 
is indicated in Figure 66. The 
two parts are connected with 
the body in such a way that the 
right hemisphere controls the 
left side of the body, and the 
left hemisphere the right side 
of the body. The cerebrum 
is the part of the brain that 
is active in thought and in the 
exercise of will powder. What 
we call the " mind " is centered 
in the cerebrum. It is the 
center which starts and con- 
trols the activity of the body. 




THE SPINAL CORD 



EiG. QQ. — The Nervous 
System. 

Showing the brain and the A long, soft, white COrd, 
spinal cord with its nerves. ^^^^^^ ^j^^ ^^.^^^ ^^^^^ ^^^^^^ 

from the lower end of the medulla (shown in Fig. 66), 
and passes down through the backbone or spine. The 
vertebrae of the backbone protect the cord on all sides. 
In other words, the spinal cord runs inside the back- 
bone (see Fig. 42, p. 125). As may be seen from Fig- 
ure 66, the cord is not of the same thickness throughout 
its length, but it becomes gradually smaller as it passes 
down the back. At the lower end it divides into fine 



THE NERVOUS SYSTEM 



193 



threads. When in its proper position inside the back- 
bone, the cord is covered not simply with bones, but 
with certain softer membranes, which act as a further 
protection, so that it is very thoroughly guarded from 
injury. 

If we cut the cord directly across, it will appear as 
we see it in Figure 67. Like the brain, it is divided by 
deep furrows into 
two parts, the 
right half and the 
left half. The fur- 
rows, as the figure 
shows, do not ex- 
tend all the way 
across the cord. 




Fig. 67. 



Anterior Root \ 

Qan^lion. 
- Two Pieces of the Spinal 
Cord. 

but the two halves Showing the gray matter and the two roots 
of the spinal nerves. Tlie arrows show the 
direction of the stimuU. 



are united at their 
center. At the 

very center of the cord. Figure 67 shows a rather irreg- 
ular mass, shaped somewhat like the letter H, with four 
arms running off to the sides. This material is of a 
dull gray color, and is called the gray matter. It con- 
tains nerve cells, which start and receive nervous im- 
pulses, or ^^ messages." Outside the graj^ matter is 
a substance, whiter and more glistening, called the 
white matter of the cord. This consists of nerve 
fibers, Avhose duty it is to carry up and down the cord 
the nervous impulses which are started and received by 
the gray matter. 



194 PHYSIOLOGY AND HYGIENE 

THE NERVES 

The brain may be regarded as the superintendent of 
the body. If this superintendent is to have any control 
over the different organs in the body, it must in some 
way be connected with them. The superintendent of 
a factory often has telephone connection witli every 
room in the building by means of electric wires which 
run in various directions. In a similar way the super- 
intendent of our body, the brain, is connected with 
every part of the bod}^ by a series of connecting fibers 
which we call nerves. 

Figure 66 shows these nerves coming from the spinal 
cord as it passes down through the back. The nerves 
start in the gray matter of the cord, and then pass from 
the cord between the vertebrae, extending outward into 
the body to connect with all the organs controlled by the 
brain. As may be seen from Figure 67, each of these 
nerves rises from the cord in two hranches^ known as 
roots. The front branch, called the anterior root, carries 
nervous impulses from the brain to the muscles ; while 
the other, the posterior root, carries nervous impulses 
from the skin and other organs to the spinal cord and 
thence to the brain. 

After the two branches unite, as shown in the figure, 
they form what we call a nerve trunk. Such a trunk 
is made up of thousands of nerve fibers, or wires, bound 
together in a bundle. Each fiber runs to a distinct 
part of the body. Figure 68 show^s a bundle of fibers 
that make up a nerve. A nerve trunk usually con- 



THE NJiEVOUS SYSTEM 



195 



H 



Medulhfy 
Sheath- 



electric current that rings the bell. 



Axis 



fm^^ 



tains some fibers that carry impulses toward the brain 
and some that carry them away from it. A few 
nerves, however, contain only one kind of fiber. By 
means of these hundreds of thousands of nerve fibers 
every muscle, every gland, every 
part of the skin, receives and 
sends nervous impulses to and 
from the brain. 

The wire that rings an electric 
bell is always connected with two 
different pieces of apparatus, with- 
out which it would be useless. At 
one end of the wire is placed the 
bell to be rung; at the other end 
there is a battery, which starts the 



i 



i '1 



NtrvQ 



The wire serves simply to connect fyHnder- 

the battery with the bell. The ^. , 

nerves in our body serve, in a Nerve 

similar way, to connect two pieces t- ^o a at 

^' ^ Fig. 68. — A Nerve. 

of apparatus placed at their ends, showing on the right a 
corresponding to the battery and nerve composed of 
the bell. 

If we could examine carefuU}^ 
the nerve fibers, we should find 

that many of tliem end in a minute, somewhat rounded 
body, Avitli numerous branches extending from it on 
all sides (Fig. 09). This body is called a nerve 
cell, and it corresponds in its work to tlie battery 
that starts the electric impulse to ring the bell. Since 



the many nerve libers 
and on the left a single 
nerve liber. 



196 



PHYSIOLOGY AND HYGIEXE 



the nerve cells are the organs that start and receive 
nervous impulses, we should expect to find them most 
numerous where stimuli are sent out to the various 
organs ; and this is the case. There are a great many 

nerve cells in the spinal cord, 
and in the brain they are so 
numerous that we cannot 
even conceive of their num- 
ber. It is estimated that 
the brain contains 9,000,000,- 
000 such cells. 

We m^ij think of one of 
these cells as a tiny battery 
which can start nervous im- 
pulses over the nerve fibers 
leading from it, or as a bit of 
apparatus which receives im- 
pulses coming over other 
nerves. Each nerve cell is 
connected by a long nerve 
fiber with some part of the 
body. There is no part of 
the body, no matter how 
small, that is not connected 
with the nerve cells of the brain and spinal cord. 

The nerve cells in the brain are, most of them, near 
the surface. The rest of the brain consists of a com- 
plex tangle of fibers running in all directions, somewhat 
like the series of wires that run into a central telephone 
station ; only instead of a few hundred such wires the 
brain has hundreds of thousands. 




Fig. 69. — A Nerve Cell. 

Showing branches and a single 

nerve fiber arising from it. 



THE NERVOUS SYSTEM 197 

QUESTIONS 

1. What is the relation of the nervous system to the rest of 
the body? 

2. What is the brain ? 

3. What are the parts of the brain? 

4. Where is the medulla? What is its work? 

5. If the cord is cut across below the medulla, why would 
breathing stop at once? 

6. What is the cerebellum ? What actions does it control? 

7. How is the cerebrum arranged? What powers does it 
control ? 

8. What is the spinal cord? Where is it situated? 

9. What does a cross section of the spinal cord show of its 
structure? 

10. What is the purpose of the nerves? 

11. If the posterior root of a nerve (see Fig. 67) were cut, could 
the person receive sensations through that nerve ? Why ? 

12. H6w do the brain and spinal cord resemble an electric 
battery ? 

13. Why are there more nerve cells in the brain than elsewhere ? 



CHAPTER XI 
THE NERVOUS SYSTEM IN ACTION 

DUTIES OF THE NERVES 

If we touch the hand with a hot match, instantly we 
have a feeling of pain and the hand is drawn away. 
The hand is connected with the brain by the nerve 
shown in Figure 70. If this nerve of the arm should 
be cut at the point indicated in the figure, and then the 
match should be touched to the hand, no pain would 
be felt. What is more, if we should wish to move the 
hand, we should be quite unable to do so. Cutting the 
nerve, tlierefore, destroys all sensation and all power 
of motion in the hand. The cutting does not injure 
the muscles. They would still be able to contract, if 
they were stimulated by an electric shock. Moreover, 
cutting does not destroy sensation ; for if the end of 
the nerve which is still attached to the brain (called 
the central end in Fig. 70) were pinched, we should 
feel pain. And what seems most strange of all, we 
should think that we felt the pain in the hand and 
fingers, although the nerve had really been touched at 
a point above the elbow. These facts teach us several 
things in regard to the action of the nerves. 

1. The nerves form a line of communication be- 
tween tlie brain and sjjinal cord and the muscles. By 
the nerves the brain causes the muscles to act. 

198 



THE NERVOUS SYSTEM IN ACTION 



199 



2. Muscles commonly act only when tliey receive a 
nervous impulse from the brain and spinal cord. 

3. Nerves form a means of communication betAveen 
the different parts of the body and the brain, by which 
messages (sensations of pain, for example) are sent to 
the brain. 

4. Sensations are really felt 
in the brain, although we seem 
to feel them in other parts of 
the body. 

The burning match touched 
to the skin of the hand causes a 
message to travel up the nerve, 
but no feeling of pain results 
unless the message reaches the 
brain. When, therefore, the 
nerve is cut or compressed so 
that the message cannot get to 
the brain, no sensa- 



tion of pain is felt. 
If the message does 
reach the brain, 
however, it produces 
pain, and we locate 
this pain in the hand 




Ntrvt 



Fig. 70. 
Showing the connection of the hand with 
the brain by a nerve. It is supposed to 
be cut above the elbow. 



where the match touched it. The brain always locates 
the pain at tlie end of the nerve which brings tlie 
message, and for tliis reason it sometimes makes a 
mistake. 

For example, the nerve from the hand luis all our 



200 PHYSIOLOGY AND HYGIENE 

lives brought messages to the brain from the hand. 
Now if this nerve is cut above the elbow, as in Figure 
70, it can no longer bring messages from the hand. But 
if the central end, also shown in the figure, is pinched, 
the nerve carries the impulse to the brain. Since the 
brain has always received over this nerve impulses 
coming from the hand, it is now not able to recognize 
that this impulse does not come from the same place. 
So the sensation seems to come from the hand, when in 
reality it started from above the elbow. 

These facts make it clear that the nerves are merely 
conducting wires carrying impulses that start at their 
ends. Some impulses start at the outer ends and 
go to the brain, producing sensation there. Other 
impulses start in the brain and pass down the spinal 
cord and out to the muscle fibers, where they cause 
motion of the muscles. Messages travel thus through 
the nerves in both directions, and by means of them 
the brain is placed in communication with every part 
of the body. 

The nerve fibers by means of which sensation is 
communicated to the brain are called sensory nerve 
fibers. Those which convey the impulses /rom the brain 
to the muscles are called motor nerve fibers. 

DUTIES OF THE SPINAL CORD AND MEDULLA 

The spinal cord has more complicated duties to per- 
form than have the nerves. Carrying messages to and 
from the brain is simply one of these manifold duties. 
As can be seen from Figure 66, large numbers of nerves 



I 



THE NERVOUS SYSTEM IN ACTION 201 

enter the spinal cord, and in the cord itself they pass 
up to the brain. These nerves are all so arranged that 
messages passing through them from the right side of 
the brain reach the left side of the body, and messages 
starting from the right side of the body reach the left 
side of the brain. 

Independent Action of the Cord. — We have learned 
that the spinal cord contains nerve cells as well as nerve 
fibers. If these nerve cells serve the same purpose as 
batteries, we should naturally expect that the spinal 
cord could do something besides simply carry messages. 
The cord does indeed have another kind of duty, called 
reflex action. If, for example, a finger is pinched, an 
impulse is started which passes to the spinal cord on 
its way to the brain. In the spinal cord it excites 
certain cells. These in turn excite other cells, from 
which instantly motor impulses are sent out from the 
spinal cord to the muscles controlling the arm and 
hand, causing contraction and the withdrawal of the 
finger. This is called reflex action, and it takes place 
very quickly — in less than one tenth of a second. 
The original sensory impulse, of course, may pass on 
to the brain, causing the feeling of pain, but the in- 
stantaneous withdrawal of the finger from danger was 
a reflex action, entirely independent of the brain action. 
Reflex action does not require an}^ will power and can 
take place just as well when a person or an animal is 
asleep as when he is awake. In the case of some ani- 
mals it will take place when the brain has been entirely 
removed from the body. 



202 PHYSIOLOGY AND HYGIENE 

A reflex action never starts itself. It must always 
be started by some outside stimulus. To produce such 
a reflex action something must stimulate the body in 
such a way as to cause a message to go to the spinal 
cord. The action never begins in the spinal cord itself, 
but always at the outer ends of the nerves, usually 
because something touches the skin or some other part 
of the body. 

Although the brain is not necessary to reflex action, 
still it is possible for the brain partly to control such 
action, especially if the action is a repeated one, or one 
of which we are aware in advance. For example, if 
the bottom of the foot is tickled, the foot is pulled 
away. This is a reflex action and will take place when 
we are asleep just as readily as when we are awake. 
If, however, we are awake and knoAv what is to be 
done, we can often use sufficient will power to prevent 
the foot from being pulled away even when it is 
tickled. The will power is exerted through the brain 
alone and, therefore, in this case the brain stops the 
reflex action. But under some circumstances, even 
when we are awake, our will power is not strong 
enough to prevent the reflex action. If a bit of food 
becomes caught in the Avindpipe, for instance, it will 
cause us to cough, and no matter how hard we try, we 
shall be unable to keep from coughing until the food is 
dislodged. The coughing is a reflex action and, in this 
case, is too strong to be controlled by will power. 

Reflex Action in the Medulla. — A study of the me- 
dulla, indicated in Figure 65 as at the top of the spinal 



THE NERVOUS SYSTEM IN ACTION 203 

cord, shows that this part of the brain controls a 
number of the most important vital functions. Here 
are centered the powers that control hreatJdng^ the 
rapidity jof the heart heat^ swallowing^ the size of the 
blood vessels (thus regulating circulation), and some 
others of less importance. These actions are all reflex. 
It will be recognized that these actions are the primary 
functions of life. If they continue, the person will 
live, even though all others cease for a time. The 
activity of the cerebellum and cerebrum may stop for a 
while and yet the person may continue to live if the 
medulla is not injured; but if the medulla is injured, 
it may stop the heart beat and breathing at once, and 
thus produce instantaneous death, even though the rest 
of the brain is uninjured. The medulla may thus be 
said to be the center of the vital functions. The cen- 
ters controlling these ^ital functions may act quite 
independently of will power or consciousness, as they 
do when we are asleep. 

THE CEREBELLUM AND CEREBRUM 

The Work of the Cerebellum. — The cerebellum controls 
reflex actions more complicated than those connected 
with the spinal cord. Such actions as walking are 
at first controlled by our will power and are not reflex 
at all. After a time, however, they become reflex in a 
measure, and take care of themselves. A\Mien we first 
begin learning to play the piano we must think care- 
fully of the action of each finger, but after playing for 
a number of years, we no longer need to attend par- 



204 PHYSIOLOGY AND HYGIENE 

ticularly to the fingers. We simply place our hands 
on the piano and the fingers fall naturally upon the 
proper keys and make the proper motions for pro- 
ducing music. A skilled pianist can talk to a friend 
and at the same time continue playing, pa}dng no atten- 
tion to his fingers and yet never striking wrong notes. 
Through long practice certain parts of his brain, prob- 
ably in the cerebellum, have learned to take care of the 
motions of the fi^ngers, so that the mind is free to 
attend to something else. Some of these complex 
actions are controlled by the cerebellum, but physiolo- 
gists as yet know little about them or where they are 
located. 

The Work of the Cerebrum. — The upper and larger 
part of the brain, the cerebrum, is the real center from 
which all the impulses of our conscious activity come. 
It is the center that regulates the conscious action of 
the whole body. 

The relation of the cerebrum to the other parts of 
the body may be best understood by the comparison 
already used, of the superintendent and the factory. 
The cerebrum itself is like the general superintendent 
who directs the work of the whole factory. The vari- 
ous centers in the cerebellum and the spinal cord are 
like the foremen of different rooms or of different parts 
of the work. When the superintendent wishes some- 
thing to be done, he sends a message to the foreman of 
a special room, and the foreman gives the order to the 
individual workmen. In this way the superintendent 
is not obliged to pay attention to the detailed work of 



THE ivTERYOUS SYSTEM IN ACTION 205 

every employee, but can give his time to planning the 
operations of the factory as a whole. 

So the mind, when it wishes some special action to 
be performed, such as moving the hand, sends a message 
to some of the centers in the lower parts of the brain, 
and these forward the necessary commands by way of 
the nerves to the muscles in the arm and hand, so that 
the hand is moved. After the various centers have 
learned their duty, the mind itself does not need to 
attend to the little details. Our minds are then free 
for thought. We can talk as we play on the piano 
because the mind has trained some of its servants 
in the cerebellum to look after the contractions which 
cause the fingers to touch the keys correctly. If these 
servants in the cerebellum are not carefully trained, the 
plans made by the mind will not be properly carried 
out. Our education, from tlie time of our earliest 
childhood, is largely given to training the servants of 
the mind. We sometimes call the training of these 
servants acquiring habits, 

THE IMPORTANCE OF HABITS 

We can readily see how necessary it is that we should 
have well-trained servants to do our work, and, there- 
fore, that we should form good habits. After we have 
once formed a habit it is very difficult to get rid of it. 
The training of children at home and at school is for 
the purpose of developing right habits of thinking and 
acting, in order that, after they become men and 



206 



PHYSIOLOGY AND HYGIENE 



women, they may be properly guided by these good 
habits. 

By doing the same thing again and again the body 
becomes so accustomed to a certain kind of action that 



I 




Fig. 71. — The Brain in Position. 

Showing the location of the different powers in the brain. 



it will be ''second nature" to perform that action. 
Every time that we do something in a certain way it 
becomes easier to do the same thing in that way again. 
If the habit is an injurious one, like the alcohol habit, 



THE NERVOUS SYSTEM IN ACTION 207 

we come more and more under its influence by yielding 
to it. If, on the other hand, the habit is a useful one, 
we fit ourselves better for life every time we perform 
the action. This is as true of moral actions as it is of 
muscular movements. If we exaggerate the facts when 
we tell a story, we are forming a habit that will grow 
until we become liars, unless the fault is overcome. If 
we dawdle over our books instead of giving our best 
thought to study, we are forming habits of inattention 
that are likely to hinder successful work through life. 
We are constantly forming habits whether we wish to 
do so or not. Inasmuch as these habits are to be our 
servants through life, it is wise to see to it that we form 
those that will be useful rather than those that may do 
us harm. 

We know very little in regard to the location of the 
different powers of the cerebrum. Figure 71 indicates 
about all that is really understood. The power of think- 
ing is probably connected with the front of the brain, 
certain powers of motion with the middle, while some 
of the senses are located in the back part of the brain. 

THE CARE OF THE MIND 

Our entire lives are directed by the mind. We 
should, then, take the best possible care of these minds 
of ours. A few facts of importance are worth remem- 
bering. 

Sleep. — We cannot continue one form of activity 
very long w^ithout some kind of rest, for both tlic body 
and tlio mind need to rest. Tlio most complete kind 



208 PHYSIOLOGY AND HYGIENE 

of rest for mind and body is sleep. When we sleep, 
the mind is largely free from its usnal forms of activ- 
ity, although our dreams show us that the mind is not 
entirely inactive. The deeper the sleep the less distinct 
will be the dreams. The amount of sleep needed by 
various people differs greatly. A young child needs 
twelve hours out of the twenty-four for sleep, a growing 
boy or girl about ten, while most grown people require 
only about seven or eight. Some persons seem to get 
on very comfortably with even less. It is best to 
remember, however, that we are much more likely to 
have too little sleep than too much. 

Sometimes a boy or girl takes a kind of pride in 
sitting up late and studying far into the night. This 
is likely to be done just before examination time, 
under the impression that better preparation can thus 
be made for the tests. This is a great mistake. Sit- 
ting up late to study, the night before, usually renders 
one less fitted to pass an examination. The many facts 
we try to cram into our heads during such midnight 
study are not all found there the next morning. We 
are weary, and the brain does not work as it should. 
To get a good night's rest is a much better method of 
preparing for an examination than to study until the 
mind gets tired. 

Concentration. — The person who accomplishes the 
most is the one who is able to turn his whole attention 
to his work. When we are thinking of several things 
at once, we can give none of them careful considera- 
tion. If, when we are supposed to be studying, we let 



THE NERVOUS SYSTEM IN ACTION 209 

our thoughts wander to the athletic field, then to the 
woods and the trout brook, then to something going on 
in the schoolroom, bringing them back finally with an 
effort to the lesson, it will take us much longer to master 
the lesson than it Avill if we give our attention to that 
and nothing else. The pupil who applies his mind 
wholly to the lesson he is preparing will do his work 
much more quickly and much better than his neighbor 
across the aisle who studies one minute and dreams the 
next. The ability to think of one thing at a time is 
largely a habit, and one of the most useful of habits. 
It is one that can and should be acquired by every boy 
and girl. If we allow our thoughts to wander from 
one thing to another, we shall let this habit master us, 
and in later life we may, as a result, find it very diffi- 
cult to think continuously and vigorously. 

Recreation. — The mind needs recreation as well as 
work and rest. It ought to be employed at times in 
such a way as to obtain relief from its required tasks. 
We ought just as much to give our minds recreation as 
to give them sleep. Without it we become dull, and 
our bodily health is likely to suffer. Recreation is 
even more necessary for the boy or girl who wishes to 
be a scholar than it is for the person who works prin- 
cipally with his muscles. 

Each of us should choose his own recreation. It 
should be something that gives pleasure and enjoyment, 
and it must be something that we do from choict\ not 
because we must. It is also necessary that tlie kind 
of recreation a person takes should oeeasionall}^ be 



210 PHYSIOLOGY AND HYGIENE 

changed. Much of a person's success as well as happi- 
ness in life depends upon his having enjoyment. We 
can work harder and do better, if we maj^ look forward 
to pleasant recreation as the reward for faithful labor. 

Dependence of the Mind upon the Body. — Our minds 
and our bodies are related so closely that their welfare 
cannot be separated. If we allow our bodies to become 
weak from lack of exercise or want of the proper kinds 
of food, our minds will not be vigorous. The most 
active mind, and the one that thinks best, will be found 
in a healthy body. The boy or girl who enjoys books 
and study is the one Avho must be especially careful to 
give proper attention to health. The student must 
have recreation, exercise, good, wholesome food, fresh 
air and sunshine, if he wishes to preserve at its best 
that valuable treasure, his mind. The boy or girl who 
neglects mind for body cannot compete in after life with 
the person who studies hard. On the other hand, the 
boy or girl who neglects bodily health for the sake of 
knowledge is sure to fall behind the one who develops 
a healthy mind in a healthy body. 

The Mind and Narcotics. — One matter of importance 
in connection Avith the proper care of the mind is keep- 
ing it free from the control of all narcotics. The use of 
alcohol has its first and most important effect upon the 
action of the brain. The first result of taking alcohol 
seems to be to excite the brain, and for this reason it is 
called a stimulant. But its chief action upon the brain 
is really the opposite of a stimulant, for almost at once 
it begins to dull the mental ijotvei^s. This dulling action 



THE NERVOUS SYSTEM IN ACTION 211 

becomes very noticeable if more than a small amonnt of 
alcohol is used. 

Careful testing has shown that one who has taken 
even small quantities of alcohol cannot add a column 
of figures so quickly as usual, or that if he can add 
the column as quickly he may fail to do it accurately. 
He may be able to talk more rapidly, but he will com- 
monly not think so clearly. He acts more slowly than 
usual. If he is hunting, he loses his straight aim ; if 
setting type, he works less rapidly and makes more 
mistakes. He is perhaps not conscious of all this, cind 
feeling somewhat excited and exhilarated, he may 
actually think that he is doing more work than usual, 
while he is really doing less. He may believe himself 
to be bright and witty, when he is uttering only foolish 
jests. The man witli whom he has business dealings, 
and who keeps sober, gets the better of him in a bargain. 
If he uses more than a comparatively small amount 
of alcohol, the dulling effect becomes so great that he 
presently notices it himself. He finds that he is unable 
to talk intelligently; he becomes confused and stupid, 
and finally is unable even to walk straight. When lie 
is completely under the influence of alcohol, nearly all 
the actions of his body cease, except breathing and the 
beating of the heart. 

There are various degrees in this dulling effect of 
alcohol. It is sli^'ht when small amounts are used, and 
complete when large quantities are taken. How large 
an amount a person can take without having his judg- 
ment seriously aff'ected it is impossible to say. Hut 



212 PHYSIOLOGY AXD HYGIENE 

even the very small amounts appear to have some 
dulling action upon the mind. Some of the keenest 
thinkers have found that their power of concentrated 
thought is dulled by taking even very small amounts 
of alcohol. 

QUESTIONS 

1. How do we know that sensations are felt only in the brain ? 

2. If the spinal cord were cut across at the shoulders, w^hat 
effect would it have on the lower parts of the body ? 

3. What have the nerves to do with sensation? 

4. What is reflex action ? 

5. Where is reflex action controlled? 

6. If a person's foot is tickled, what action and reflex action 
OQCur? Do you suppose the foot would be pulled away if the 
person were asleep ? 

7. What reflex actions are controlled by the medulla? 

8. What kind of reflex actions are controlled by the cerebellum ? 

9. Why should vou think coughing to be a reflex action? 

10. What are the duties of the cerebrum ? 

11. Why is it important that good habits be formed ? 

12. In what ways can the mind be cared for ? 

13. Why is sleep necessary ? 

14. If a person goes to sleep while sitting up, he is likely to fall 
over. Why is this? Would he be as liable to fall over as he 
would be if he fainted ? 

15. Why should w^e learn the habit of concentration? How 
may it be learned? 

16. What is recreation? Why is it necessary? 

17. What is the effect of alcohol upon the mind ? 



CHAPTER XII 
THE SENSES 

The brain is shut up tight in its bony box, the skull. 
It has no direct contact with the external world, and 
yet it succeeds in finding out very well what is going 
on outside of our bodies, just as a telegraph operator, 
shut up in his little office, can learn what is going on 
in the world. As we have learned, the brain is con- 
nected with the outer parts of the body by the sensory 
nerves, whicli bring messages, or impulses, from the 
exterior. They extend from every part of the body to 
the spinal cord and the brain, and bring messages from 
every part. The messages, when they reach the brain, 
produce what are called sensations, and it is through 
the sensations that we get our knowledge of the outer 
world. 

There are several outside forces that may excite the 
sensory nerves to send impulses to the brain. One of 
the most common of these is a touch upon the skin, 
which sends an impulse that gives rise in the brain to 
a sensation which we call touch. Similar sensations 
can come from every part of the skin. There are also 
several forces capable of starting impulses through spe- 
cial nerves. Lights for example, starts impulses from 
the eye through its nerve, soioui from the ear. ThriUigli 

213 



2U 



PHYSIOLOGY AND HYGIENE 



these special nerves Ave get our sense of sight and of 
hearing. Some substances excite impulses from the 
tongue, giving a sense of taste, and others from the 
nose, giving the sense of smell. These act by means 
of special organs, situated at tlie ends of particular 
nerves, which we call sense organs. These four senses 
are known as the special senses. 



THE SENSE OF SIGHT 

The Eyeball. — The eye itself is shaped like a ball, as 

showm in Figure 73, although as we look at it in a person's 

. . face it appears quite 

-^- ' unlike a sphere. This 

is because we see only 
a small portion of the 
front of the eye, the 
rest being hidden be- 
hind the eyelids. The 
only part of the eye- 
ball that we can see is 
just what appears be- 
tween the eyelids, and 
the eye will look 
large or small accord- 
ing to whether the eyelids are wide open or parti)' 
closed. Different people appear to have eyes of vari- 
ous sizes, but the dimensions are really always about 
the same ; that is, the diameter is close to one inch. 

The eyeballs are set in deep sockets in the front 
of the skull, as may be seen from Figure 73, only the 




Fig. 72. — The Eye, viewed from in 

Front. 
Showing the tear gland and tear duct. 



THE SENSES 215 

front surfaces being exposed. The sockets protect the 
balls from injuries which might come from blows. 

The Eyelids. — Two folds of skin hang over the eye, 
one above and the other below, as may be seen in Figure 
73. These are eyelids, which open and close over the 
eye. When closed, they serve to protect the eye and 
also to keep its surface clean and moist. Even when we 
are awake the eyelids close every few seconds. We are 
quite unconscious of this movement of the eyelids, but 
we can easily observe it by watching the eyes of some 
one near us. The front of the eye is extremely delicate, 
and if the lids did not constantly cleanse its surface, 
and if the tear secretions did not wash the dust away, 
the eye would become inflamed, and the sight be affected. 
The eyelids, by means of their long lashes and their 
exceedingly quick motion, serve also to guard the eye 
against accident. The hairs on the edges of the lids, 
called the eyelashes, assist in keeping out the dust. 

The Tear Gland. — The lids are aided in keeping the 
eyes clear by the tears. A small lachrymal gland, or 
tear gland, is lodged just above each eye, on the side 
away from the nose. This gland produces a watery 
liquid, which flows down over the eye and keeps its 
surface moist. The liquid flows over the eyeball to 
the inner edge of the eye near the nose, where there is 
a tube, tbc tear duct, leading to the cavity inside the 
nose, as shown in Figure 72. The tears, after washing 
the surface of the eye, pass through the duct into the 
nose and the tliroat, and are then swaUowed. Tsu- 
ally the gland produces just liquid enough to wash the 



216 



PHYSIOLOGY AND HYGIENE 



eyeballs and to pass easily down the lachrymal duct. 
But when a person cries, the tears are produced so 




Neri^e 



EiG. 73. — The Eye, viewed from the Side. 
Showing its shape, the socket, and the attachment of muscles. 

rapidly that they cannot all pass through the duct into 
the nose. They then overflow and run down the cheeks. 

The Eye Muscles. — Six small muscles are attached to 
each eyeball to move it. One is on the top, one on the 
bottom, one on each side, and two others have an oblique 
position. Figure 73 shows the form and position of 
these muscles. By the contraction of the muscles the 
eyeball can be turned in any desired direction. 

Structure of the Eyeball. — If we examine a photog- 
rapher's camera, we find that it has three chief parts. 
There is (1) a dark chamber^ the box of the camera, 
closed so as to admit light only from the front. In the 
opening in front which admits the light there is (2) a 
lens^ which makes an image of the object to be photo- 



THE SENSES 



217 



graphed ; at the back of the camera is (3) the sendtive 
plate^ upon which the picture is taken. 

The human eye is made upon much the same plan 
as the camera, although differing in details. Like the 
camera, it has a dark 
chamber and a lens, and 
also a sensitive surface 
at the back. If we ex- 
amine Figure 74, we can 
see how closely the eye 
and the camera may be 
compared. The eyeball 

is a dark chamber^ which, \"~"_\~jSt\, _ y^^^^ 

like the camera, admits 
light only from the 
front. At the point 
where the light is ad- 
mitted there is a lens^ 
shown in Figure 74, and 
at the back of the eyeball is a sensitive surface called 
the retina, show^n in Figure 75. Between the front of 
the eye and the retina the eyeball is filled with trans- 
parent liquids, through which the light can easily pass. 

Light enters the eye from the front, passing through 
the small opening know^n as the pupil (Fig. 75\ 
Just inside of this pupil is a transparont lens. The 
lens is so shaped that the rays of light are changed in 
tlieir direction and come together at tlie back ])art of 
the eye. When they come together they produce a 
little picture or image of the objects from which the 




Fig. 74. — A Comparison of the 
Structure of the Camera and 
THE Eye. 



218 



PHYSIOLOGY AND HYGIENE 



light comes. This image is simihxr to what we see on 
the ground-glass screen at the back of a photographer's 



Aqueous^ 
JHumorj 



Jtrotk 




f(erye 



Fig. 75. 



-A Diagram representixg a Section through 
THE Human Eye. 



camera, which shows a picture of the objects toward 
which the camera is pointed. In the same way a little 
picture is formed upon the back part of the eye. The 
part of the eye upon which the image is formed is the 
retina, and is the sensitive part. 

The retina is full of nerves, and in some wonderful 
way, not fuUj^ understood, these nerves send impulses 
to the brain, by which the brain receives and recognizes 
the picture. If the nerves that connect the eye with the 
brain were cut, the message could never reach the brain, 
even though the image should be formed on the retina. 
If the eye were injured so that the image could not be 
formed on the retina, we could not see, even though the 
nerve were in good condition. 



THE SENSES 219 

The lens that forms the picture on the retina is not 
able to form a picture of both a near and a distant 
object at the same time ; hence we cannot see clearly 
near objects and distant objects at the same moment. If 
we are observing a hill some distance off, and wish to 
look at a pencil in our hands, the shape of the lens 
changes a little so that the pencil becomes sharply 
pictured on the retina, but, at the same time, the hill 
necessarily becomes blurred to our sight. 

Nearsightedness. — If the eyeball is of exactly the 
right shape, ordinary objects will be sharply pictured 
upon the retina. If, however, the ball is a little too 
long, distant objects will not be clear, not sharply 
focused as we say, but they will look blurred. A per- 
son with such eyes cannot see distant objects clearly, 
though he can readily see objects quite close to the 
eyes. We say he is nearsighted^ and, in order to see 
clearly, he is obliged to wear glasses especially prepared 
to overcome his difficulty. 

Nearsightedness is very common. It is often due to 
improper habits of study. We are likely to lean over 
a desk or a table when we read, thus bringing the book 
very close to the eyes. This habit, if continued, is 
certain to cause such changes that the eyes, which at 
first could see clearly, become little by little so affected 
that only near objects can be clearly seen. Such near- 
sightedness is quite common among people who spend 
their early years in study. Tlie difticulty is less com- 
mon among those who live out of doors and who do 
little or no reading. If we will take pains to sit erect 



220 PHYSIOLOGY AND HYGIENE 

when reading or studying, and to liold our books no 
nearer than a foot or eighteen inches from the eyes, we 
shall greatly reduce the tendency to nearsightedness. 
If we lean over our work, holding a book within six 
inches of the eyes, we shall be quite sure to develop 
nearsightedness. 

Color BHndness. — Some people have the sense of 
color poorly developed, and we call them color blind. 
This does not mean that they cannot see any color at 
all, but that they confuse the various colors. The 
most common form of color blindness is the inability 
to distinguish clearly reds from greens. Since red and 
green are the colors used as signals on railroads and 
steamboats, a pilot or a railroad engineer who cannot 
distinguish them readily may commit such blunders 
that accidents will result. Persons who are to hold 
responsible positions on railroads or steamboats are 
accordingly required to have their eyes specially tested 
for color, and no one who is color blind should ever 
think of taking such a position. The difficulty is more 
common among men than among women, and no remedy 
for it is known. 

Care of the Eyes. — 1. The eyes were made to be 
used, and it does them no harm to exercise them con- 
stantly. If, however, they are used on work that 
requires close attention, such as reading or sewing, 
they become tired and should frequently be allowed a 
moment for rest, such as is gained by closing the eye- 
lids or by looking at distant objects. 

2. ' We should not abuse the eyes by reading in a 



THE SENSES 221 

dim or flickering light. Nor slioulcl a bright light, like 
the sun's rays, be allowed to fall upon the page we are 
reading. We should never look directly at a bright 
light. 

3. The only proper position for holding the head 
when we read is erect. Reading, when lying on the 
back or in a hammock, is very injurious to the eyes. 
We must not forget, moreover, that using the eyes 
means also working the brain. When the brain is 
tired, one is often inclined to lie down and read a book 
— setting the tired brain to work again, and under 
conditions bad for the eyes themselves. 

4. If a child has difficulty in seeing objects clearly, 
his eyes should be examined by an oculist. Headaches 
are frequently due to trouble with the eyes, and if a 
child has a tendency to headache, his eyes should be 

■ examined. It frequently happens that the trouble 
with the head may be cured by the use of glasses pre- 
scribed by a competent oculist. 

5. Particles of dust that get into the eyes are 
usually carried off with the tears by way of the 
tear duct, and a few winks remove them. If this is 
not sufficient, the trouble may frequently be remedied 
by lifting the upper eyelid witli the fingers and drawing- 
it down over the lower eyelid. If this does not remove 
the particle of dust, it may be taken out by son^ie com- 
petent person Avho can })ass gentl}' over tlie eyeball the 
end of a soft handkerchief rolled up to a point. If tliis 
attempt fails, a pliysician should be called. Tlie eyes, 
in such cases, should 7}ever he ruhhcd. The eves are 



222 



PHYSIOLOGY AND HYGIENE 



organs too delicate and too important to be treated by 
incompetent persons. If one has trouble of any kind 
with his eyes, he should consult a physician or an 
oculist. 

THE SENSE OF HEARING 

The Ears. — The two projections on the sides of the 
head, which we commonly call the ears, have very lit- 




Ncrve, 



£udachian 
Tube., tot he 
throat 

Fig. 76. — The Ear. 

A section through the " stony bone," showing the parts of the ear. 

tie to do with hearing. They are only bits of carti- 
lage covered with skin, which serve, perhaps, to col- 
lect Avaves of air, and probably make sounds a little 
louder. The real hearing organ is the inner, or true 
ear, which is wholly inside the head and embedded in 
the bones. The ear itself is in the middle of the 
hardest bone in the body, called the stony bone. The 



THE SENSES 223 

ear is thus more thoroughly protected from external 
injury than any other organ. 

The ear is a very comp>licate(l organ. Its general 
structure may be seen from Figure 76, which shows a sec- 
tion through the side of the head, giving the chief parts 
of the ear. The passage from the outside to the true 
ear, as the figure shows, is slightly bent. In it there is 
secreted a little wax, which helps keep it moist and flexi- 
ble. The passage is closed at the inner edge by a mem- 
brane which is stretched across. This is the tympanic 
membrane. Is is tough and elastic. Earache in chil- 
dren is usually caused by sores in the ear ; these occa- 
sionally make little holes through the membrane, which 
interfere somewhat with hearing. Sometimes very loud 
noises, like explosions, break the membrane and make 
the person deaf. 

Figure 76 shoAvs that beyond the membrane tliere 
is a cavity. It is known as the ear drum, or tympanic 
cavity, and is also sometimes called the middle ear. 
The ear drum is filled wdth air, wdiicli enters it througli 
a tube in the lower side. This tube leads to the 
throat, as indicated in Figure 76, and is opened every 
time we swallow. In this w^ay the drum is filled with 
air, and the pressure of the air in the drum is kept the 
same as the pressure of tlie air outside. If tliis tube 
becomes closed, as sometimes happens wlih intlanima- 
tion of throat or nose, the air within the ear is partly 
absorbed, so that the pressure inside becomes less and 
the membrane is pushed in by the pressure of ilie out- 
side air. This affects the hearing injuriously. This 



224 PHYSIOLOGY AND HYGIENE 

is the reason why throat troubles are very apt to extend 
to the ears and interfere with hearing. Indeed, the 
most common cause of deafness is to be found in diffi- 
culties of the throat. Catarrh in the throat is one of 
the first things that a physician attends to in most cases 
of difficulty in hearing. 

In Figure 76 it will be seen that three small bones 
(malleus, incus, and stapes) are stretched across the 
cavity of the middle ear. The outer of these ear bones 
is attached to the membrane and the inner one con- 
nects with the inner ear, which contains the real hearing 
organ. In this inner ear are many nerves. Sound is 
produced by waves of air which enter the ear and shake 
the tympanic membrane. This shakes the bones at- 
tached to it, and by their motion the effect of the air 
wave is transferred to the inner ear, where it reaches 
the nerves. This shaking or vibration upon the nerves 
starts nervous impulses which travel rapidly to the 
brain. When the messages reach the brain they pro- 
duce a sensation which we call hearing. 

Hearing. — Our ears tell us very little in regard to 
sounds except their loudness or softness, and their 
pitch (high or low). Our power of determining dis- 
tance is limited. If we know what causes a certain 
sound, we can determine something of its distance by 
the loudness. We judge the distance simply by the 
loudness of the sound as compared with what we should 
hear if the sound were nearer or farther away. If, 
for example, we hear the whistle of a locomotive, and it 
sounds faint, we are sure that the engine must be a long 



THE SENSES 225 

distance away, because we know tl\at the sound itself is 
really very loud. If, on the other hand, we hear the 
buzz of a mosquito, and it sounds loud, we know that 
the insect is close to the ear. We can determine the 
distance of sound in no other way than by the compara- 
tive loudness. 

Our power of determining the direction from which 
sound comes is not much greater. Noises coming to 
the ear from the side of the head may sound louder in 
one ear than they do in the other, and in that case we 
judge that the sound is on the side of the head where it 
seems loudest. Sometimes we unconsciously turn the 
head around a little, until we find that the sound appears 
to be loudest when the head is in a certain position. 
We then conclude that the noise comes from the direc- 
tion toward which the ear is turned. But this test is 
by no means accurate. 

Care of the Ears. — The ears require very little care. 
The use of solid objects, like pins or needles, to remove 
the ear wax is very unsafe. The ears may be kept suffi- 
ciently clear of wax by means of the little finger, which 
should be pushed downward as it is placed in the open- 
ing. Very loud sounds close to the head are likely to 
do harm. Boxing children's ears is liable to injure the 
membranes within. Pain in the ear maj^ sometimes be 
relieved by placing hot cloths upon the ear ; but if it 
persists, a physician should be called. It is well to re- 
member that deafness is most commonly produced by 
throat troubles, and if one has any difficulty in hearing, 
he should first of all look to the condition of his throat. 



226 PHYSIOLOGY AND HYGIENE 

Slight deafness is not "unusual with children ; it renders 
a pupil apparently inattentive and dull. The cliild does 
not realize that he has any difficulty in hearing, and 
very likely neither his teacher nor his parents suspect it. 
Therefore a child who is inattentive should have his 
hearing tested. If deafness is the cause of the difficulty, 
a physician should be consulted at once to remedy the 
defect, if possible. 

THE SENSE OF TASTE 

By the sense of taste we learn something of the nature 
of liquids. Solid substances do not produce taste. It 
is true that many solid bodies have a certain taste, when 
taken into the mouth, but not until they are more or 
less dissolved in the saliva. If we rub the tongue dry, 
and then place upon it a lump of sugar, we notice no 
taste at first, but, as soon as the liquids of the mouth 
begin to dissolve the sugar, we perceive the sweet taste. 

Location. — The sense of taste is located in the mouth, 
but not, as is commonly supposed, wholly in the tongvie. 
The upper side of the tongue has a sense of taste, but 
the under side has not. Besides this, the roof of the 
mouth, especially at the back, has a sense of taste. When 
a substance is rolled around by the tongue at the back 
of the mouth, we find there the strongest sense of taste. 

The Tongue. — The tongue of a healthy person is of a 
pinkish red color. If it is otherwise, the stomach is 
probably out of order. One of the simplest methods 
employed by physicians for detecting signs of certain 
diseases is an examination of the tongue. When this is 



THE SENSES 



227 



covered with a whitish or yellowish coating, or when it 
is bright red, the physician knows that something is 





If we examine the tongue carefully, we find that it 
appears much as in Figure 77. It is covered with 
numerous little bunches 

or papillae, which differ - Papillae withtosU buds j-^^^-j 

in appearance and vary 
in use. Some of them, 
particularly those at the 
back of the mouth, are 
associated with the sense 
of taste and are called 
taste buds (see Fig. 77). 
The tongue itself is 
made up principally of 
muscles, which run in 
many directions and 
enable us to move the 
tongue very easily. In 
addition to the muscles 

there are glands which secrete a watery material that 
keeps the tongue moist. There are also many bhH)d 
vessels and nerves, among them some Avhicli are 
particularly connected with taste, and which carry to 
tlie brain the messages that enable us to determine the 
presence of sweet, sour, or bitter substances in the 
mouth. 

Tastes. — We tliink of the substances that we eat 
as having many different tastes. All kinds of tastes 



EiG. 77. — The Tongue. 
Showing the papilloe on its surface. 



228 PHYSIOLOGY AND HYGIENE 

may, however, be classified under four heads, — bitter, 
sweet, acid (sour), and salt. These different tastes are 
not perceived equally well in all parts of the mouth. 
We taste sweet things most delicately at the tip of 
the tongue, and bitter things at the back part of the 
mouth. We are very apt to confuse tastes and smells, 
and many sensations that we call tastes are really 
tastes and smells combined. When we drink a glass of 
soda water, for example, we have the sweet taste of the 
sirup, but the gases from the soda water pass into the 
nose and produce a very strong sense of smell. The 
two together are what we call the pleasant taste of 
the soda water. Many other so-called tastes are largely 
smells, as can be tested by blindfolding a person, hold- 
ing his nose so that he cannot catch the odor, and then 
giving him successively small pieces of apple, onion, 
and potato. 

Duration of the Sense of Taste. — Our sense of light 
is gone at almost the instant the light ceases to shine 
into the eye, and the sense of sound stops as soon as the 
vibration that produces it ceases or becomes too distant 
to affect the ear. The sense of taste, however, does 
not cease so quickly, but it may last many seconds, or 
even several minutes, after the substance tasted has 
been swallowed, partly because some of the substance 
remains in the mouth. An unusually bitter taste, like 
that of quinine, may last as long as half an hour. 

The sense of taste easily becomes tired, and in this 
respect it is quite different from the sense of sight. We 
may use our eyes all day long, and yet see as clearly at 



THE SENSES 229 

night as in the morning. But, if we continue to use our 
sense of taste for even a few minutes, it k^ses its acute- 
ness. We can test this characteristic by eating a lemon. 
Food does not have so pleasant a taste at the close of a 
meal as at its beginning, so we often finish our dinner 
Avith a highly flavored dessert to please our taste, which 
has by this time become dull. 

Our sense of taste is one of our greatest enjoyments, 
but to obtain the most pleasure from it we must not 
gratify it too much. If we live upon plain food, with 
an occasional luxury, we shall find more enjoyment in 
it than do people who are constantly eating highly 
flavored foods. The luxury gives special pleasure only 
when it is unusual. If we should eat the most delicious 
food constantly, it would soon come to give us less 
enjoyment. The bulk of our food should be such as 
satisfies the appetite rather than the taste. Finely 
flavored substances, like candies, sauces, and sweets in 
general, should be used in comparatively small quanti- 
ties, if we wish to enjoy them as much as possible. 

THE SENSE OF SMELL 

The sense of smell enables us to determine the pres- 
ence of certain gases. Only substances that are in the 
form of a gas or vapor can be smelled. Rose water is a 
liquid, but the only part that we smell is the vapor that 
rises from it. The amount of vapor required to excite 
the sense of smell is exceedingly minute. If a bottle of 
peppermint oil be opened for a few moments, it will give 
off a vapor that will fill the room and will be smelled 



230 



PHYSIOLOGY AND HYGIENE 



Olfactory 
Nerves 



by every one present. Yet if tlie bottle of liquid be 
weighed in the most delicate scales, there will be no 
perceptible difference in the weight before and after the 
bottle was opened. No other sense is as delicate as that 
of smell. 

Location. — The sense of smell is located in the cavities 
of the nose. The two nostrils lead into two large cavi- 
ties above the mouth, 
separated from each 
other by a bony parti- 
tion. The cavities 
extend backward to 
the throat. They are 
partly filled with large, 
thin, folded bones, 
which bend around so 
as to form curved sur- 
faces. They give a 
large amount of ex- 
posure to the air, as it 
passes over them. 
Upon these bones are the nerves of smell (olfactory 
nerves), as shown in Figure 78. Vapors entering the 
nose, as we breathe, act upon these nerves in such a 
way that they send messages to the brain, and produce 
in the brain the sensation that we call odor or smell. 

Its Use. — The sense of smell in human beiiigs is not 
so well developed as in some animals, or so useful. We 
may occasionally notice by its aid the presence of inju- 
rious gases, such as illuminating gas wdiich is escaping 




Fig. 7: 



A Vertical Sectiox of the 

Nose. 
Showing the nerves of smell. 



THE SENSES 231 

from a burner. Sometimes, also, we perceive through 
the sense of smell the presence of some body or substance 
which gives off a special odor, but which is concealed 
from our eyes. With other animals the sense of smell 
is much more keen than it is with human beings. A 
dog can follow his master's footsteps by means of his 
very keen sense of smell. 

The acuteness of the sense of smell is blunted by con- 
tinued use even more than is that of taste, as we can 
readily prove with cologne or other strong odor. The 
first whiff of cologne on a handkerchief gives a strong 
sensation. If, however, we bury our face in the hand- 
kerchief and continue to breathe the odor, we cease to 
smell the cologne. In order to perceive it again, we 
must remove the handkerchief from the nose and let 
the smelling organs rest for a time. 

OTHER SENSATIONS 

We frequently say we have five senses, — seeing^ liear- 
ing^ tasting^ smelling^ ^nd feeling. The first four of these 
are quite distinct. The fifth, which we call feeling, is 
made up of several different kinds of sensations. There 
are really two different senses in the skin, — touch 
and temperature. In addition to these the term fccJ'nig 
usually covers the pain sense, hunger, thirst, and some 
otlier sensations. 

The Touch or Pressure Sense. — ^The skui is sensitive 
to the touch or pressure of objects. Whenever a sub- 
stance presses even very lightly upon the skin it excites 
the nerves in such a way that nervous impulses are 



232 PHYSIOLOGY AND HYGIENE 

sent to the brain, AA^iich builds out of these impulses an 
impression, more or less distinct, of the object that 
touched us. We can easily test this by shutting our 
eyes and letting some one touch us with different kinds 
of unknown objects. The whole skin is thus an organ 
of touch, although it is more sensitive in some places 
than in others. 

Through the messages that come to the brain from 
the skin we not only get a sensation that the skin is 
touched, and that the object touching it causes a cer- 
tain amount of pressure, but we know quite accurately 
what part of the body is in contact with the object. 
We can tell whether the ring is on the finger or is lying 
on the palm of the hand, and whether it is on the little 
finger or the thumb. The delicacy with which we can 
determine where the skin is touched differs very much 
on different parts of the body, as can be easily discov- 
ered by experiment. It is most delicate at the tips of 
the fingers and the tip of the tongue. We can tell 
within a twenty-fifth of an inch where an object, like a 
needle point, touches the skin of the finger tips or the 
tongue. The sense of location is much less delicate on 
the back of the fingers, and still less so on various parts 
of the arms and shoulders. Upon the back of the shoul- 
ders it is least delicate of all ; in fact, we cannot deter- 
mine within two and a half inches where an object 
touches the back part of the shoulder. We can see 
from this that the parts of the body most used are the 
ones in which the sense of touch is the most delicate. 

It is the sense of touch, or of location of touch 



■^ 



THE SENSES 233 

sensations, that gives us our most intimate knowledge 
of the nature of objects outside our bodies. By the 
sense of touch alone we can tell whether such objects 
are rough or smooth, whether they are blunt or sharp, 
whether they are solid or liquid. 

The Temperature Sense. — When a warm body touches 
the skin, nervous impulses go to the brain, and we have 
a feeling of warmth. The skin, in general, is sensitive 
to both cold and heat, though some points on the skin 
are sensitive to heat and not to cold, while others are 
sensitive to cold and not to heat. The warm and 
cold spots are very close together, so that a body no 
larger than the head of a pin will in some places touch 
both. Every part of the body has a certain tem- 
perature, and if some object warmed to that exact 
temperature touches the skin, the pressure of the object 
will be felt, but it will seem to be neither warm nor 
cold. If, how^ever, the object is a little warmer than 
is the skin at the point where it touches, it will seem 
warm ; if it is a little cooler than the skin at that 
point, it will seem cold. The temperature of the 
skin is not just the same on all parts of the body. 
The temperature of the hand is usually a little lower 
than that of the forehead, so that an object which feels 
warm to the hand may feel cool to the forehead. The 
forehead itself feels warm to tlie hand. 

If we step in cold weather from a carpet to a bare 
floor, the floor feels colder to tlie feet tlian the carpet, 
although the two are actually of the same temperature. 
The bare floor draws the heat away from the feet more 



234 PHYSIOLOGY AND HYGIENE 

rapidly than the carpet does. Any object feels cool 
when it takes heat away from the body rapidly. If it 
withdraws no heat from the body, we feel that the 
object touches the skin, but we feel no sensation of cold 
resulting from the contact. Some substances draw heat 
more rapidly than others, and this is why, in cold 
weather, for example, metal objects seem colder than 
cloth to the touch. 

Sense of Pain. — Almost any nerve which carries mes- 
sages to the brain will carry a sense of pain, if it is 
strongly excited. If the pain is slight, we can deter- 
mine very closely where it comes from ; but if it is 
severe, we cannot locate it so accurately. A slight 
toothache, for example, can be located in the proper 
tooth, but when it is severe, it seems to come from the 
entire jaw, or the whole side of the head. Occasionally 
the whole upper part of the body appears to be in pain, 
although the trouble is confined to a single tooth. 

We find it hard to realize that pain is of any use, but 
it really is of great value. If it did not hurt to burn 
the fingers, children would get their fingers so badly 
burned as to render them useless. In fact, they would 
probably destroy the fingers entirely before they were 
old enough to, know how to take care of themselves. 
Pain thus warns us to guard our bodies from accidents 
and disease, and to keep them in as good a condition as 
possible. Pain is a warning to our bodies, and we should 
heed it as carefully as does the engineer the danger 
signal beside the railroad track. 






THE SENSES 235 

The Muscle Sense. — We seldom hear any one speak 
of the muscle sense, but it is really of considerable im- 
portance. It is the sense by which we know when and 
how much we contract our muscles. Even when we 
shut our eyes we can move our fingers very accurately, 
knowing almost exactly how much the muscles contract. 
Let us say, for example, that we will allow one hand to 
rest upon the table while we close our eyes. If, while 
our eyes are still closed, another person lifts the hand, 
we can tell very accurately by means of the muscle 
sense how far it has been lifted. This sense is of great 
importance, for it enables us to control our actions and 
to move our muscles together. If we could not feel 
how much we move the muscles, we could not possibly 
make the body motions that require the contraction of 
a number of muscles at the same time, as when Ave 
throw a stone. The muscle sense is not situated in 
any particular place, but is present in all parts of the 
body, especially in the joints. 

QUESTIONS 

1. How does the^. brain get a knowledge o^f the world? 

2. What are the chief sense organs ? 

3. What is the shape of the eyeball, and where is it located? 

4. What are the eyelids? What is their purpose? 

5. Where are the tear glands located? What is their use? 
G. How are the eyeballs moved? 

7. What are tht> principal parts of the eye? 

8. Why is it d(^sirable to sit eriH't wIumi r^^uling? 

9. li" the lens of the eye should beconu^ opaijue. \vh:it would be 
the result? 



236 PHYSIOLOGY AXD HYGIENE 

10. Some persons cannot distinguish between green and ripe 
cherries. Can you explain the reason? 

11. In what five ways should we care for the eyes? 

12. Where are the real hearing organs ? 

13. What are the important parts of the ear? 

14. How do the ears enable us to hear ? 

15. How should we care for the ears? 

16. If two colors are mixed, do we get a new color? If two 
sounds are mixed, .do we get a new sound or do we hear both 
sounds ? 

17. If you close the nose and swallow, what effect is produced 
in the ears? Can you explain why? 

18. Where is the sense of taste located? 

19. AYhat is the structure of the tongue ? 

20. Mention several duties of the tongue? 

21. What may be said of the duration of the sense of taste? 

22. Where is the sense of smell located? How may this sense 
be dulled? 

23. How could you tell w^hether soda water, wdthout sirup, has 
a taste or only a smell ? 

24. W^hat three sensations compose the sense of feeling? 

25. What is the use of the touch or pressure sense ? 

26. AVhat do we learn from the sense of heat and cold ? 

27. Lay the palm of the hand upon the cheek. Does the hand 
appear warm or cool ? Do the same upon the forehead. What do 
you observe? 

28. Of what use is pain ? 

29. Of what importance is the muscle sense ? 



CHAPTER XIII 
HEALTH AND DISEASE 

The body is a very delicate piece of machinery, as we 
can readily appreciate. It needs to be treated carefully, 
but most of us have bodies that will keep in good 
condition if we care for them properly. 

The Body cures Most of its Own Ills. — The human 
body is such a beautifully constructed machine that it 
will of itself take care of the ordinary slight illnesses. 
If we have a cold, the body soon cures it ; wounds are 
rapidly healed ; broken bones are mended ; digestive 
troubles usually disappear. All of these little maladies 
the body itself can care for. We need simply to do 
our part toward keeping in good condition by eating 
plain, wholesome food, taking plenty of exercise, and 
living as much as possible out of doors in the fresh air 
and sunshine. 

Many people have the idea that the proper way to 
treat ailments of all sorts is to take medicines. This is 
a great mistake. Medicines cannot cure disease. Tlie 
most they can do is to aid the body to right itself. 
Most people would be better off by letting nature cure 
their little ailments, giving her the aid that comes from 
such simple remedies as baths, soaking the feet in hot 
water, and rubbing, rather than by dosing themselves 

237 



238 PHYSIOLOGY AND HYGIENE 

with drugs. Medicines should be used only under a 
physician's guidance. The constant use of drugs rather 
weakens than strengthens the general physical powers. 
If people used fewer drugs and more common sense, 
took less medicine and more exercise, wore fewer wraps 
in winter and spent more time out of doors, we should 
hear less about sickness, and the whole race would be 
more robust. 

Disease. — When the machinery of the body is out of 
order we speak of the condition as sickness or disease. 
The causes of diseases are numerous. Sometimes thej^ 
are the result of improper food habits, or intemperance, 
of breathing impure air, or of other improper conditions 
of life. One class of very important diseases is pro- 
duced by parasitic animals or plants growing in the 
body. 

Some diseases we say are ^' catching," by which we 
mean that one person very readily gets the disease from 
another. This class includes such diseases as measles, 
scarlet fever, mumps, whooping cough, etc. Such dis- 
eases are called contagious. Another class of troubles, 
like rheumatism, malaria, etc., are non-contagious, since 
healthy persons do not " catch " them from sick people. 

PARASITIC DISEASES 

Contagious diseases are probably all caused by very 
small animals or plants that get into the human body 
and multiply there. Most of them are so small that 
they can be seen only with the aid of a very powerful 
microscope. 



HEALTH AND DISEASE 239 

Parasitic Animals. — There are a few animal parasites 
that occasionally get into our bodies and cause trouble. 
One of these is the tapeworm^ which enters the body 
from raw or insufficiently cooked beef or pork. It lives 
in the intestines and makes considerable trouble, al- 
though it is not usually very dangerous. Another such 
parasitic animal is the trichina^ which also comes from 
eating pork, not properly cooked, such as rare or 
slightly cooked ham or sausage. The disease resulting 
is violent and painful, and often causes death. The 
simple method of avoiding both tapeworm and trichina 
is to eat no meat that is not thoroughly cooked. 

Another form of animal parasite produces malaria^ or 
chills and fever. This parasite is a minute animal, to 
be seen only through a microscope, which gets into the 
body, usually from the bite of the mosquito. Certain 
kinds of mosquitoes are liable, when they bite, to leave 
in the skin some of these little parasites. The best 
way to protect ourselves against malaria or chills and 
fever is to keep from being bitten by mosquitoes. 
This may be done generally by covering the doors and 
windows of our houses Avith mosquito netting, particu- 
lar care being taken to remain behind such netting at 
night. 

Parasite Bacteria. — The most important of the para- 
sites that make their way into the body are a type of 
plant called bacteria. These minute plants are so small 
that a powerful microscope is required to see tliem, and 
so light that they can easily float around in the air in 
the form of dust. They are very abundant everywhere. 



240 PHYSIOLOGY AXD HYGIENE 

Some of them, instead of being harmful, are directly 
useful to us. Bacteria cause the souring of milk and 
the decay of meat ; they produce vinegar the flavor of 
butter and cheese, and they prepare the soil for the 
growth of plants. These tiny parasites are, on the 
whole, very useful friends of ours. 

But while some bacteria are healthful, others, which 

may live as parasites in our bodies, produce certain 

I * diseases. Some of these 

(V' are shown in Figure 

/Jf J'y ^ 79. Typhoid fever ^ con- 

I Ayr Cho/tra ^mj> ^^'^^P^ion (tuberculosis), 

"^ y n.'^-fL • diphtheria, and boils and 

'ypf^oid^Sj^ produced by them. 

Other contagious dis- 
%^S^^^^ eases, like measles^ scar- 



^"^^soo ?^^ fever ^ jnumps^ and 

Absct^S whoopiiig cough^ are 

Fig. 79. -Bacteria THAT PRODUCE probably causcd either 
Certain Diseases. 

by bacteria or by some 

other microscopic parasites. Eacli of the different dis- 
eases is produced by its own kind of bacteria. 

Protection against Harmful Bacteria. — Bacteria can- 
not ordinarily injure us unless they get inside the body. 
We have already seen how the skin forms a covering 
which protects the body from the entrance of external 
objects, and this commonly keeps out dangerous bac- 
teria. So well are we protected that the majority of 
them do no harm whatever, because they do not obtain 



HEALTH AND DISEASE 241 

entrance to the body. We need not be frightened, 
then, because bacteria are present in milk and water, 
for this is the natural condition. The bacteria in milk, 
and also those in water, are usually, though not always, 
harmless. 

Even if the bacteria of diseases do find their way into 
the body, it does not necessarily follow that they will 
effect injury. The human body is able to fight these 
bacteria, and in many cases to destroy them before they 
do harm. When we are in the best condition of health, 
our power of resisting them is greatest, and conse- 
quently we are then less liable to take some contagious 
diseases than when we are in a more or less weakened 
state. In general, the best method of avoiding all bac- 
terial diseases is to keep in robust health, although 
even perfect health apparently cannot protect one 
against taking some contagious diseases. Robust 
health, as we have seen, depends upon plain, whole- 
some food, plenty of fresh air and outdoor exercise, 
and living a regular life. 

Immunity from Contagious Diseases. — ^Nlany conta- 
gious diseases, such as smallpox, scarlet fever, mumps, 
chicken pox and yellow fever, are rarely taken by the 
same person more than once. In some way, which Ave 
do not fully understand, the first attack acts upon the 
body so that it is able to resist the action of the para- 
sites ever afterward. A person who has had one attack 
of such a disease is said to be immuiie to future attacks. 
Advantage is taken of this fact by vaccinaticm, by which 
we are protected against smallpox. When vaccination 



242 PHYSIOLOGY AND HYGIENE 

"• takes," it causes what is really much like a mild form 
of smallpox, which makes us for a certain time immune 
to that disease. 

Prevention of Contagious Disease. — The best way to 
check the spread of contagious diseases is to prevent 
the distribution of the bacteria that cause them. If we 
can keep these minute growths from passing from one 
person to another, we can frequently stay the spread of 
the disease. The rules adopted by the boards of health 
in our cities, especially in connection with schools, are 
made for the sake of preventing the spread of bacteria. 
That is why persons having contagious diseases, such 
as diphtheria, are placed in rooms by themselves. That 
is why children are not allowed to attend school when, 
for example, a member of the family has the measles. 
In general, the regulation of these matters may be left 
to boards of health, but there are a few facts which it 
is well for us all to understand. 

How Bacteria get out of the Body. — When a conta- 
gious disease is '\taken" from a person by another, 
the bacteria which produce the disease must have 
passed from the body of the patient to that of the other 
individual. Usually, the bacteria pass from the body 
of the sick person in some of the secretions or excre- 
tions. If the disease is accompanied by sores, such 
as boils, the bacteria leave the body in the discharges 
from the sores. If there is an eruption from the 
skin, as in scarlet fever and measles, the bacteria prob- 
ably leave the body from the skin, as well as from the 
discharges of the mouth and nose. If there is a dis- 



HEALTH AND DISEASE 243 

charge from the digestive canal, as in typhoid fever, 
bacteria find exit with what passes from the bowels. If 
the disease is in the mouth or throat, as in diphtheria, 
bacteria will usually be found in the saliva. If it is 
in the lungs, as in consumption, we may look for the 
bacteria in the saliva and phlegm coughed up by the 
patient. If the disease is accompanied by a cough, as in 
whooping cough, we may regard the breath during the 
coughing as carrying the bacteria. 

How Bacteria are Carried. — 1. Many of the dis- 
charges from patients get into sewage through drains 
and closets. Hence the sewage of a city is almost sure 
to contain hosts of dangerous bacteria, and it should 
be disposed of in the safest and most careful manner 
possible. If it enters a river, and the water of the 
same river is used for drinking, many cases of typhoid 
fever are almost sure to arise. Most of the sewage of 
a city enters into common sewers, and each house is 
connected with these sewers. It is necessary, there- 
fore, to have means for preventing the bacteria in the 
sewers from entering the house. This is accomj^jlished 
by properly devised plumbing, AVe can thus compre- 
hend the importance of having and keeping tlie 
plumbing of a house in good condition. 

2. Bacteria may be transferred by contact, eitlier 
actual contact with a patient or with soniclhing that 
he has touched. A nurse may get bacteria upon her 
hands from handling tlie patient or his clothing. If 
she washes her hands frequently and refrains from put- 
ting her fingers to her mouth, the danger from eonta- 



244 PHYSIOLOGY AXD HYGIENE 

gion will be largely reduced. Other persons in the 
house may take a contagious disease by using spoons, 
knives, forks, cups, or saucers which have been em- 
ployed in the sick room. Bacteria cling to such arti- 
cles, and may thus be transferred to any person using 
the dishes. The danger may be avoided by allowing 
no one to use the same eating utensils as the sick per- 
son, or by washing them thoroughly in boiling water 
before they are used by others. Bacteria are also fre- 
quently left by sick persons upon door knobs, stair 
rails, etc., and these should, therefore, be carefully 
washed. In general, it is an excellent rule always to 
wash the hands before eating, and to avoid eating food 
which has been handled by others. 

3. Bacteria may be carried by the air. When the 
skin peels, as in scarlet fever, or when there is a skin 
eruption, as in smallpox, the germs probably pass into 
the air, and may thus be carried to other persons. The 
same is true of diseases with which there is a cough, 
such as whooping cough and consumption. It is not 
very easy to guard against this danger if we must stay 
in the same room w^ith the patient ; but the danger may 
be reduced, as much as this is possible, by insisting 
upon a constant supply of fresh air in the sick room. 
The germs, after floating in the air for a while, settle 
with the dust. Every time the room is swept or dusted 
they are stirred up again. Sweeping and dusting 
schoolrooms increases the chance of the spread of con- 
tagious diseases. So far as possible, wiping with damp 
cloths should replace sweeping and dusting. After the 



HEALTH AND DISEASE 246 

bacteria have reached the out-of-door air, most of them 
are killed by the sunshine, although this is not true of 
the bacteria of all diseases. 

4. Uncooked food sometimes distributes disease bac- 
teria. This applies chiefly to water and milk. Water 
from a river receiving city sewage is the most common 
source of typhoid fever. Milk is occasionally the source 
of diphtheria, scarlet fever, typhoid fever, or diarrhoea. 
In case of epidemics from water, we may protect our- 
selves by having the water boiled before we drink it. 
The only protection against disease carried by milk is 
either to buy the milk from reliable sources or to boil 
it before it is usedo Other foods which we eat un- 
cooked, such as lettuce, celery, raw oysters, and fruit, 
are occasionally sources of disease. Cooking is an 
efficient safeguard against the danger. 

6. Occasionally flies or other insects may carry 
disease germs, particularly those of cholera, typhoid 
fever, and some eye diseases. The chief precaution to 
be taken is, as far as possible, to prevent flies from 
alighting on our food or eating utensils. AVe have 
already learned that mosquitoes distribute malaria, 
and it is also true that they carry yellow fever. 

Every one should bear in mind a few simple rules 
which, if followed, will help to prevent the spread of 
contagious diseases. They are partieuhirly important 
in schools wliere children from many families are 
brought together. 

Do not spit on the floor or sidewalk. 

Do not put pencils or penholders into the mouth. 



246 PHYSIOLOGY AND HYGIENE 

Do not put the fingers in tlie mouth. 

Do not put money in the mouth. 

Never put into the mouth anything that another per- 
son has had in his mouth (gum, bean blowers, whistles, 
drinking cups, etc.). 

When coughing turn the face away from otliers, and 
avoid allowing others to cough in your face. 

Wash the face and hands often. 

By these means we may largely avoid the germs 
which might get into our bodies. 

THE USE OF ALCOHOL 

We have learned in previous pages that alcoholic bev- 
erages are quite unnecessary to health, and are in many 
cases extremely harmful. They interfere to a large 
extent wdth the perfect health and happiness of man- 
kind. The question might naturally be asked. Why is 
it that people learn to use alcoholic beverages when 
these are not only of no use, but liable to do so much 
injury ? There are three main reasons : — 

(1) The boy does not realize the risk he is running. 
He does not expect that he will become addicted to the 
use of alcohol in such a way as to injure him. Com- 
monly he does not know the danger that lies before him. 

(2) The boy sometimes knows well enough that 
alcohol is dangerous and likely to do him harm, but 
he thinks it manly to drink^ and is afraid of being called 
odd or priggish if he does not. But it is not manliness 
that causes a boy to follow his companions into a 
saloon. On the contrary, it is usually cowardice. He 



HEALTH AND DISEASE 247 

is afraid that he may be laughed at. It is really the 
manly and courageous boy who dares to stay outside 
and to refuse to follow others into useless danger, and 
in the end his associates never fail to recognize and to 
admire his real courage and manliness. 

(3) The third reason is the desire to he sociaL The 
boy finds that his companions drink beer, and he feels it 
more social to follow their lead, even at the cost of some 
danger to himself, than to oppose them, especially if they 
are a little older than he. He should remember that 
the kind of sociability that leads to a saloon, or into 
any other useless danger, had better be shunned. There 
is companionship far pleasanter than that which comes 
through a glass of beer, and there are friends more use- 
ful than those who invite one to a saloon or urge one to 
join ill a social glass. 

Reasons why Alcohol should be entirely avoided as a 
Beverage. — The only wise course is to let alcohol en- 
tirely alone. There are three important reasons for 
so doing : — 

(1) It may do us physical harm. It is impossible 
for any one to tell where the injurious effects begin, or 
to say how much he may use Avitliout harm to himself. 
Small quantities are liable to lead to larger ones, and 
the habit of using alcohol is apt to cause an appetite 
which will result in untold evil. The only safety lies 
in avoiding alcoholic beverages altogether, ^huiv a 
person who seemed strong-willed has to his sorrow 
found his will power insulVicient to resist the craviiui 
which alcohol has developed. 



248 PHYSIOLOGY AND HYGIENE 

(2) The constant use of alcohol^ even in moderate 
amounts, frequently lowers one's moral tone and intelli- 
gence and thus interferes luitli one's ehance of success. The 
parts of the city which show the greatest poverty are 
the parts which abound in saloons. Prisons are filled 
with men and women who have used alcohol. The use 
of alcohol not only means the waste of large amounts 
of money, but if continued, it has a tendency to reduce 
a person's chance in life. It frequently ruins ambition ; 
it tends to destroy the power of attending strictly to 
work; it makes a man careless about fulfilling his 
responsibilities, and is likely to lead to loss of employ- 
ment. Some corporations, especially railroads, refuse to 
put into responsible positions, such as those of engineers 
and switchmen, persons who use alcohol even ^' in mod- 
eration," or occasionally. It is therefore not simply 
those who use alcohol to excess who risk their chances 
of filling responsible positions. The use of alcohol is 
likely to bring a boy into a circle of acquaintances who 
will injure rather than benefit him. It is likely also, 
when he has become a man, to destroy his interest in 
his family and all that is good, and to lead him to live 
a life upon a low plane. 

(3) Our example will infliience others. We all have 
some responsibility for those about us, and to lead 
another, by our example, into a course of life that in- 
jures him, is a very serious thing, the results of which 
we cannot measure. When people see their friends 
using alcohol, apparently without being injured by it, 
they are very likely to think that they can do the 



HEALTH AND DISEASE 249 

same. They may be led to use alcohol in excess, from 
seeing others use it in moderation. The moderate 
drinker is the one whom others try to follow. He is 
thus in a measure responsible for the downfall of the 
friend who, weaker than himself, tries to follow his 
lead. 

The healthy boy or girl does not need alcoholic drinks 
and is better off without them. In using them he is 
running the risk of injuring his own chances of success 
in life, and an even greater risk of ruining the chances 
of his neighbor or friend. To live a clean life one's 
self, and to help others do the same, is the best means 
to happiness and success. 

THE DUTY OF PRESERVING HEALTH 

It is our duty to make the most of our opportunities 
in life. Whether we decide upon a business career or 
a profession, we are sure to find that, in the sharp com- 
petition of to-day, a good body and abundant physi- 
cal health are wonderful aids in reaching the greatest 
success in life. Physical strength will give one power 
to become a leader among men. Failure to develop 
our powers to their highest extent will result in a life 
unsatisfactory to ourselves. It is our duty to set our 
ambitions high. There is no one who may not hope 
for success, and no one who should not endeavor to live 
a broad and useful life. The liigher we aim, the higher 
the position we shall reach. It is perfectly right and 
honorable to determine to reach a responsible })osition 
in business, to acquire wealth and power, and to become 



250 PHYSIOLOGY AND HYGIENE 

a person of influence. These things are possible to 
every American youth who will make proper use of his 
opportunities. Without perfect health, however, suc- 
cess is likely to slip from the grasp. One of the best 
assurances for a successful life is a well-developed, 
active, healthful body. 

We should remember that the body is a marvelous 
machine. Its value depends upon its being in a condi- 
tion of the greatest efficiency. A locomotive with a leak- 
ing valve may still pull a few cars, but it is much less 
useful than a perfect engine. So our bodies, even when 
more or less out of order from abuse of one sort or 
another, may still keep alive and carry on some of the 
duties of life ; but they will do less work than when 
they are in perfect condition. 

The value of the human body as a machine is lowered 
by every form of overmdulgejiee. Intemperance in eat- 
ing, in talking, in playing, or in working reduces our 
chances of future success. Intemperance in eating and 
drinking injures digestion ; intemperance in talking 
clestroj^s confidence in our statements ; intemperance 
in playing makes a boy unready for the more serious 
duties of life ; intemperance in workings makes him 
tired and dull. The study of our body teaches that 
any kind of indulgence results in a general lowering 
of the powers of body and mind, and makes us less 
capable of achieving the liighest end in life. 

The study, of these pages has resulted in showing 
that two great fundamental laws for developing a 
perfect body and living a useful life are : — 



HEALTH AND DISEASE 2o1 

(1) Use every poiver you possess. 

(2) Avoid the overindulgence of all appetites and all 

desires, 

QUESTIONS 

1. What is the purpose of medicine ? 

2. Why should medicine be avoided as much as possible ? 

3. What causes most contagious diseases ? 

4. What is meant by parasitic animals? 

5. How are tapeworms and trichinae taken into the human sys- 
tem? What is the result with each? 

6. How are malarial organisms taken into the body? ^ 

7. How can the body best be protected against injurious 
bacteria ? 

8. How may the spread of contagious diseases be prevented? 

9. How do the injurious bacteria pass from a person who has 
sores or boils? Scarlet fever or measles? Typhoid fever? 

10. In what important ways may bacteria be carried ? 

11. Why should plumbing be kept in good condition? 

12. How may bacteria be transferred through contact? 

13. How may bacteria be carried in the air? 

14. AVhy is wiping with a damp cloth better than dusting in a 
schoolroom ? 

15. How may bacteria in food be destroyed ? 

16. How can we reduce the danger of taking a disease dis- 
tributed by coughing? 

17. How may we prevent diseases being spread by insects? 

18. Why should we have light and air in our sleeping rooms? 

19. What three conditions most connuonly lead a person to use 
alcohol as a beverage ? 

20. Why should alcohol be entirely avoided as a beverage? 

21. What are the two fundamental laws of iieahh antl use- 
fulness ? 



CHAPTER XIV 

WHAT TO DO IN EHERQENCIES 

There are many times when a knowledge of simple 
methods of procedure in case of accident is of great 
advantage, and occasionally such knowledge may be 
the means of saving life. Some possible emergencies, 
with the proper treatment, have been mentioned on 
various pages of this book. 

Drowning. — See page 120. Dislocations, — See page 140. 

Burns, — See page 177. Foreign Bodies in the Eye. — 
Broken Bones. — See page See page 221. 

132. Freezing. — See page 178. 

Treatment for Poisoning. — The treatment to be fol- 
lowed when one swallows poison varies with each kind 
of poison. Tlie ordinary course should consist of 
three steps, although with certain poisons one of these 
may be omitted. In every case of poisoning a pHy- 
sician should be sent for at once. Until he arrives there 
are in most cases two things to do: (1) cause vomiting, 
and (2) administer an antidote to the poison. 

1. Induce immediate vomiting so as to remove as 
much as possible of the poison from the stomach. This 
may be done by giving a teaspoonful of powdered mus- 
tard in a glass of warm water. After the mustard has 
been swallowed, tickle the back part of the throat with 

252 



WHAT TO DO IN EMERGENCIES 258 

the finger or a feather. If vomiting does not occur at 
once, repeat the dose in about ten minutes. Common 
salt will sometimes serve in the place of mustard if the 
latter is not at hand. 

2. Administer some antidote to counteract the effect 
of the poison which remains in the body. The anti- 
dote to be used depends upon the poison. The most 
comxmon poisons and their antidotes are given below. 
In their treatment vomiting should be induced, unless 
otherwise stated. 

Acid poisons, like sulphuric acid (oil of vitriol), nitric 
acid (aqua fortis), muriatic acid^ oxalic acid^ carbolic 
acid^ etc. In these cases the vomiting should be 
omitted, and three or four spoonfuls of soda or of 
baking powder should be given to neutralize the acid. 
Limewater or even soapsuds may also be used. Oxalic 
acid and carbolic acid, even when neutralized, remain 
poisonous. The services of a physician are needed to 
wash out the stomach. 

Arsenic is an ingredient of paris green, many fly 
powders^ and green paints. Mix some tincture of iron 
with baking powder and give the patient a spoonful 
of the brownish poAvder which appears. Admin- 
ister every minute or two. 

Lead. — Found in sugar of lead, white lead used 
by painters, tinfoil of tobacco coverings, etc. Ad- 
minister a strong solution of Epsom salts or Glauber's 
salts. 

Mercury. — Found in corrosire sublimate, used for 
various purposes, chiefly as a disinfectant. Omit try- 



254 PHYSIOLOGY AND HYGIENE 

iiig to induce vomiting and administer the white of an 
egg^ or flour beaten up with milk or water. 

Opium. — In laudanum^ jjaregoric^ soothing sirups^ 
cholera mixtures^ etc. Give strong coffee or aromatic 
spirits of ammonia (fifteen drops of the ammonia every 
few minutes). Use all means to keep the patient 
moving and to prevent his sleeping. 

Strychnine. — Use chloroform or ether to relieve the 
violent spasms. Aromatic spirits of ammonia or 
bromide of sodium may be used, five grains of the 
latter every half-hour. Artificial respiration may be 
necessary. 

The after-treatment for poisoning must be such as to 
combat dangerous symptoms which have arisen. This, 
however, must be left to a physician, and cannot be done 
without special knowledge of medicine. 

Snake Bites. — The bites of poisonous snakes are not 
very common in this country. In biting, the snake 
forces a very violent poison into the flesh, which is 
soon carried over the body through the circulation. 
The first thing to do is to tie a handkerchief around 
the limb that is bitten, above the bite, and then insert 
a stick inside the handkerchief, twisting the stick so as 
to compress the blood vessels and stop the flow of 
blood. This will prevent the poison from flowing with 
the blood over the body. The wound should then be 
sucked to remove as much of the poison as possible. 
The poison does no injury in the mouth and no harm to 
the person who sucks it, if care is taken to empty the 
mouth at once. If the wound does not bleed, it should 



WHAT TO DO IN EMERGENCIES 2oo 

be cut open to induce bleeding. Strong coffee should 
then be given, or a large dose of whisky. 

Bites of Animals. — The bites ef animals are liable to 
be poisonous. All such wounds should be thoroughly 
washed, and as a precaution against poisoning they 
should be rubbed with nitrate of silver or cauterized 
with a hot iron. It should be always remembered that 
a bite from the teeth of any animal is more likely to 
be serious than almost any other kind of wound. 

Stings of bees and other insects may be relieved by 
placing a piece of cold mud on the spot. A weak solu- 
tion of carbolic acid, one part to twenty of water, sopped 
on with a cloth, is useful. Common ammonia is also 
sometimes efficient in relieving the pain. If the sting 
is left in the wound, as is likely if it comes from a 
honeybee, it should be removed with the sharp point 
of a knife blade. 

Mosquito bites may be commonly relieved by the use 
of ammonia water or carbolic acid solution, one part to 
twenty of water. 

Cuts and wounds should first be carefully cleansed by 
washing them thoroughly with water that has been 
boiled, and if necessary should be cleansed further 
with a brush that has also been boiled. The wound 
may then be washed with diluted carbolic acid (one 
part of acid to twenty parts of water), or \\ ith strong 
alcohol, whisky, or brandy. A compress of cUnui cU)tli, 
that has been baked to destroy germs, slionhl then be 
placed over the Avound, covering it completely from the 
air and the germs in the air. 



GLOSSARY OF TECHNICAL TERMS 



Abdomen. — The lower cavity of the body, containing the stomach, 

intestines, and other organs. 
Albumen. — One of tlie proteids, such as the white of egg. 
Anterior root. — The brancli of each nerve of the spinal cord which 

carries messages from the brain to the muscles. See Fig. 67. 
Aorta. — The large artery carrying pure blood from the heart. See 

Fig. 21. 
Aqueous humor. — One of the transparent liquids of the eye. See Fig. 

75. 
Arterial blood. — Blood that has been purified by passing through the 

lungs. 
Artery. — A blood vessel carrying blood away from the heart. 
Artificial breathing. — Breathing produced by moving a patient's arms 

and chest without action on his part. 
Auricles. — The chambers of the heart that receive blood from the 

veins. See Fig. 24. 
Axis cylinder. — The central thread in a nerve fiber. See Fig. 68. 

Bacteria. — Very minute plants, usually in the form of rodlike fibers. 

Ball-and-socket joint. — A joint that allows of free motion in all direc- 
tions. See Fig. 53. 

Biceps. — The front muscle of the upper arm. See Fig. 55. 

Bicuspids. — Eight of the teeth, of which four are in each jaw, 
between the canines and the molars. See Fig. 9. 

Bile. — The liquid secreted by the liver. 

Bladder. — The sac which temporarily holds the kidney secretion. 

Blood corpuscles. — Small solid bodies found in the blood. See Fig 20. 

Blood heat. — The ordinary temperature of the body -98.6^ F. 

Brain. — The central organ of the nervous system, located in the skull. 

Breastbone. — The bone in front of tlie chest. See Fig. 42. 

Bronchii. — The branches of the windpipe, one entering each lung. 
See Fig. 83. 

257 



258 GLOSSARY OF TECHNICAL TERMS 

Callosities. — Parts of the epidermis thickened as the result of friction. 
Canines. — Four teeth just back of the incisors. See Fig. 9. 
Capillaries. — The small blood vessels thpit connect the arteries with 

the veins. See Fig. 25. 
Carbon dioxide. — The gas which results from the burning of carbon 

in oxygen. 
Carpals. — The wrist bones. See Fig. 42. 
Cartilage. — The tough, flexible material that forms the softer part of 

the skeleton. See Figs. 33, 42, and 50. 
Casein. — A proteid contained in milk, the basis of cheese. 
Cells. — The microscopic bits of living matter of which the whole body 

is composed. 
Cereals. — Food materials obtained from grains, such as wheat, oats, 

rice, etc. 
Cerebellum. — The back part of the brain. See Fig. 65. 
Cerebrum. — The highest and largest part of the brain. See Fig. 65. 
Chest, or thorax. — The cavity within the ribs which holds the lungs 

and the heart. See Fig. 38. 
Choroid. — The middle coat of the eyeball. See Fig. 75. 
Chyle. — The name given to food in the intestines after it is thoroughly 

digested. 
Chyme. — The name given to the food mass when it leaves the 

stomach. 
Clavicle. — The collar bone. See Fig. 42. 
Coagulation. — A change from a liquid to a solid condition that occurs 

in some liquids, such as the change that takes place in the white 

of an egg when it is heated. 
Coccyx. — A small bit of bone at the low^er end of the spinal column. 
Contagious diseases. — Diseases which one person may *' catch '^ from 

another. 
Cords. See Tendons. 
Corn. — A thickened portion of the epidermis, usually on the toes, 

caused by friction or pressure. 
Cornea. — The transparent covering of the eye, in front. See Fig. 75. 
Cranium. — The rounded part of the skull containing the brain. See 

Fig. 44. 

Dermis. — The inner layer of the skin. See Fig. 61. 

Diaphragm. — A tough muscular membrane separating the thorax 

and abdomen. See Fig. 38. 
Dislocation. — The wrenching of bones out of position at a joint. 



GLOSSARY OF TECHNICAL TERMS 259 

Distilled liquors. — Liquors made by separating alcohol from a fer- 
mented substance. 

Duct. — A slender tube by which secretions are carried from a gland. 
See Fig. IL 

Dyspepsia. — The name given to certain diseases of the digestive 
organs. 

Ear-drum. — The middle cavity of the ear. See Fig. 76. 

Enamel. — The outer, hard covering of the teeth. 

Epidermis. — The outer layer of the skin. See Fig. 61. 

Epiglottis. — The lid covering the opening of the windpipe in the 

throat. See Fig. 12. 
Epithelium. — A layer of cells covering various internal and external 

surfaces of the body. 
Eustachian tube. — A tube leading from the middle ear to the mouth. 

See Figs. 12 and 76. 
Excretions. — Waste materials that pass out from the body. 
Exhalation. — Breathing air out of the lungs. 

Facial bones. The bones forming the face. See Fig. 44. 
Fat cells. — Minute drops of fat, such as exist in meat. See Fig. 2. 
Femur. — The bone extending from the hip to the knee. See Fig. 42. 
Fermentation. — A change occurring in sugar solutions by which 

alcohol is produced. 
Fermented liquors. — Drinks made from simple fermented material. 
Fibula. — The small bone in the leg below the knee. See Fig. 42. 
Foramen ovale. — The opening from the middle ear into the inner ear. 

See Fig. 76. 
Frontal bone. — The bone forming the forehead. See Fig. 44. 
Fuel foods. — Foods used for developing heat and energy. 

Gall-bladder. — A sac which collects bile secreted by the liver. See 

Fig. 13. 
Ganglion. — A knot of nervous matter containing nerve cells. See 

Fig. 67. 
Gastric juice. — The digestive fluid secreted by the glands of the 

stomach. 
Glottis. — The opening from the throat into the windpipe. See Fiir. 12. 
Glucose, or grape sugar. — Sugar found, or similar to that found, in 

fruits. 
Gluten. — A proteid derived from wheat and some other substances. 



260 GLOSSARY OF TECHNICAL TERMS 

Gray matter. — A substance containing nerve cells, found in the brain 

and the spinal cord. 
Gullet. See (Esophagus. 

Hair follicles. — The little pockets from which hairs grow. See Fig. 62. 
Hard water. — Water containing some mineral substance, usually lime. 
Hemispheres. — The two halves of the cerebrum. See Fig. 66. 
Hinge joint. — A joint in which the bones move in one direction only. 
Humerus. — The bone extending from the shoulder to the elbow. See 
Fig. 42. 

Ilium. — One of the bones of the pelvic girdle. See Fig. 42. 

Incisors. — The eight middle front teeth. See Fig. 9. 

Incus. — One of the bones of the ear. See Fig. 76. 

Inhalation. — Breathing air into tlie lungs. 

Intestine. — The long tube through which the food passes after leaving 

the stomach. See Fig. 13. 
Iris. — The membrane surrounding the pupil of the eye. See Fig. 75. 
Ischium. — One of the bones of the pelvis. See Fig. 42. 

Kidneys. — The organs for taking from the body the waste products 
found in the urine. See Fig. 60. 

Lachrymal duct. — The duct which carries tears from the eyes to the 
nasal cavity. See Fig. 72. 

Lachrymal gland. — The gland which secretes the tears. See Fig. 72. 

Lacteals. — Small tubes which carry fat from the intestine to the blood 
vessels. See Fig. 16. 

Larynx, or " Adam^s apple." — An enlarged part of the windpipe con- 
taining the vocal cords. See Fig. 12. 

Ligaments. — Bands of a white connective substance, w^hich join bones 
together. See Figs. 51 and 52. 

Ligature. — A band drawn tightly around some part of the body, as, 
to stop bleeding. See Fig. 30. 

Lime. — A mineral substance required for making bone. 

Liver. — A large red gland lying near the stomach. See Fig. 13. 

Lungs. — Two organs in the chest cavity which absorb oxygen and get 
rid of carbon dioxide. See Figs. 33 and 37. 

Malleus. — One of the bones of the ear. See Fig. 76. 
Mandible. — The jawbone. See Fig. 44. 



GLOSSARY OF TECHNICAL TERMS 261 

Marrow. — A fatty material in the middle of the long bones. See 

Fig. 45. 
Medulla. — The lowest part of the brain. See Fig. 65. 
Medullary sheath. — Covering of the axis cylinder in a nerve fiber. 

See Fig. 68. 
Mesentery. — A sheet of tissue v^rapped around the intestines and 

filled v^ith blood vessels. See Fig. 16. 
Metacarpals. — The bones betv^een the wrist and the fingers. See Fig. 

42. 
Metatarsals. — The bones between the ankle and the toes. See Fig. 42. 
Milk-teeth. — The first teeth of children, which are later replaced by 

the permanent teeth. 
Molars. — The large back teeth, twelve in number. See Fig. 9. 
Muscle fibers. — The microscopic threads of which muscles are made. 

See Fig. 58. 
Myosin. — A proteid contained in lean meat. 

Narcotic. — A drug which dulls body action. 

Nerve cells. — Minute bodies at the ends of nerve fibers, which cause 

and receive stimuli. See Fig. 69. 
Nerve fibers. — The microscopic threads of which nerves are composed. 

See Fig. 68, 
Nerves. — Long bundles of fibers which carry messages in the body. 

Occipital — The bone forming the back of the skull. See Fig. 44. 
(Esophagus, or gullet. — A tube extending from the throat to the 

stomach. See Fig, 13. 
Oxidation. — A union of some substance with oxygen. 
Oxygen. — A gas forming about one fifth of the air. 

Palate. — The roof of the mouth. 

Pancreas. — A large gland which secretes a fluid to digest proteids, 

starches, and fats. See Fig. 13. 
Pancreatic fluid. — The fluid secreted by the pancreas. 
Parasites. — Animals or plants which live on or in the bodies of other 

animals or plants. 
Parietals. — The bones forming the sides of the cranium. See Fig. 44. 
Parotid glands. — The salivary ghmds in front of the ears. See Fii:-. 1 1 . 
Patella. — A round bone in front of the knee. See Fig. 42. 
Pelvis, or pelvic girdle. — The hip bone. See Figs. 38 and 42. 



262 GLOSSARY OF TECHNICAL TERMS 

Petrous bone. — The very hard bone which contains the ear. 
Phalanges. — A name given to the bones of the fingers and toes. 
Pillars of Fauces. — Two curtain-like sheets between the mouth and 

the throat. See Fig. 10. 
Pores. — The small openings in the skin through which sweat passes. 
Posterior root. — The branch of each nerve of the spinal cord, which 

carries messages from the muscles and skin to the brain. See 

Fig. 67. 
Proteids. — Foods which are useful for building body tissue, such as 

albumen, gluten, etc. 
Pubis. — One of the bones of the pelvic girdle. See Fig. 42. 
Pulmonary artery. — The artery which carries blood from the heart 

to the lungs. See Fig. 23. 
Pulmonary circulation. — The circulation of blood from the heart to 

the lungs and back. 
Pulse. — A wave of pressure which passes along the artery with each 

heart beat. 

Radius. — One of the bones of the forearm. See Fig. 42. 

Reflex actions. — Actions which take place without the exercise of 

will. 
Rennet. — A ferment secreted by the stomach, which curdles milk. 
Retina. — The sensitive surface at the back of the eyeball. See Fig. 75. 

Sacrum. — The part of the spinal column between the hips. 

Saliva. — The secretion, produced by the salivary glands, that moistens 
the mouth. 

Salivary glands. — The glands which secrete saliva. See Fig. 11. 

Scapula. — The bone of the shoulder blade. See Fig. 42. 

Sclerotic. — The outer coat of the eyeball. See Fig. 75. 

Secretions. — Materials produced by glands for the use of the body. 

Sensory nerves. — Nerves which carry the messages to the brain, re- 
sulting in sensations. 

Skull. — The bony box which holds the brain. 

Spinal cord. — The part of the nerve system which extends down 
within the backbone. See Figs. 43 and 66. 

Spinal nerves. — Nerves rising from the spinal cord. 

Spine. — The name given to the backbone. 

Spleen. — A small gland in the abdomen, whose function is uncer- 
tain. See Fig. 13. 



GLOSSARY OF TECHNICAL TERMS 268 

Sprain. — The tearing or straining of ligaments at a joint. 

Stapes. — One of the bones of the ear. See Fig. 7(3. 

Sterilizing. — Heating some substance until all living organisms (bac- 
teria) are destroyed. 

Sternum. — The breastbone. See Fig. 42. 

Stimulant. — A substance which excites some part of the body into 
unusual activity. 

Stimulus. — A shock which causes a muscle or other organ to act. 

Suspensory ligament. — A thin band that holds the lens of the eye in 
position. See Fig. 75. 

Systemic circulation. — The circulation in all of the body except the 
lungs. 

Tarsals. — The ankle bones. See Fig. 42. 

Taste buds. — The organs of taste in the tongue. 

Tear gland. See Lachrymal gland. 

Tendons. — Bands of white substance uniting muscles with bone. See 

Fig. 56. 
Thorax. — The chest. 
Throat. — A cavity back of the mouth into which mouth and nose open. 

See Fig. 12. 
Tibia. — The large bone extending from the knee to the ankle. See 

Fig. 42. 
Tonsils. — Two rounded bodies at the back of the mouth. See Fig. 10. 
Trachea. See Windpipe. 

Tubules. — The tubes in the kidney that secrete urine. See Fig. 00. 
Tympanic cavity. See Ear-drum. 
Tympanic membrane. —A membrane stretched across the passage 

leading into the ear. See Fig. 76. 

Ulna. — One of the bones of the forearm. See Fig. 42. 

Urea. — The chief waste product of muscle action, secreted by the kid- 
neys. 

Ureter. — The duct leading from the kidney to the bladder. See Fig. (UX 

Uvula. — A small piece of the soft palate hanging downward from the 
back of the mouth. See Fig. 10. 

Vaso-motor nerves. — A series of nerves controlling the size of the 

small blood vessels. 
Vein. — A blood vessel carrying blood toward the heart. 



264 GLOSSARY OF TECHOTCAL TERMS 

Venous blood. — Blood made impure by gathering up the waste of the 
body. 

Ventricles. — The chambers of the heart that send blood into the 
arteries. See Fig. 23. 

Vermiform appendix. — A small projection from the end of the large 
intestine. See Fig. 13. 

Vertebras. — The bones forming the backbone. See Fig. 43. 

Vertebrates. — Animals possessing backbone and vertebrae. 

Villi. — Little projections on the inside of the intestine for absorbing 
food. See Fig. 17. 

Vitreous humor. — One of the transparent liquids of the eye. See Fig. 
75. 

Vocal cords. — Two membranes in the larynx whose vibrations pro- 
duce the voice. 

White nerve matter. — That part of the nervous system composed 

mostly of nerve libers. 
Windpipe, or trachea. — The tube leading from the throat to the lungs. 

See Fig. 12. 



INDEX 



Abscesses, 240. 
Acid poisons, 253. 
Air, as a distributor of bacteria. 
244. 

Need of fresh, 117. 

passages, 105. 

sacs, 108. 
Albumen, 14. 
Alcoliol, 27, 100, 184. 

Appetite for, 70, 186. 

Use of, 30, 69, 86, 101, 184, 
246-249. 
Ale, 29. 

Antidotes to poisons, 253. 
Appetite as a guide, 68. 
Arsenic poisoning, 253. 
Arteries, 83, 87, 91. 

Location of, 89. 
Artery, Pulmonary, 84. 
Artificial breathing, 121. 
Auditory nerve, 224. 
Auricles, 83. 

Backbone, 126, 133. 
Bacteria, 25, 163, 239. 

how carried, 243. 

how they get out of the body 
242. 

Protection against, 240. 
Baking, 77. 

powder, 78. 
Ball-and-socket joints, 138, 139. 
Bananas, 23. 
Baths, 172, 237. 

Cold, 172. 

Hot, 175. 



Beans, 23. 

Beef tea, 74. 

Beer, 29. 

Beets, 23. 

Biceps muscle, 141. 

Bicuspid teeth, 38. 

Bile, 54. 

Bites of animals, 255. 

Bladder, 156. 

Bleeding, 90. 

how stopped, 91. 
Blisters, 158. 
Blood, 80. 

Circulation of, 80. 

Clotting of, 93. 

Impure, 89. 

Pure, 89. 

Kespiratory changes in, 113. 
Blood vessels, 87. 

of lungs, 108. 

of skin, 100, 162. 

Regulation of, 97, 191, 203. 
Blushing, 99. 
Boiling, 57, 76. 
Boils, 240. 
Bones, 124, 128. 

Broken, 132, 237. 

Carpal, 125. 

how held together, 136. 

List of, 152. 

IMaterial for, IS, 128. 

INIisshapon, 130. 

of children, 129. 

Structure of, 128, 
Bowels, 53. 

Brain, 9(}, \)\\ 145, 166, 189, 190. 
265 



266 



INDEX 



Brandy, 30. 
Bread raising, 78. 
Breastbone {see Sternum). 
Breathing, 110. 

and exercise, 115. 

Artificial, 121. 

Center of, 191, 202, 203. 

Purpose of, 113. 

through mouth, lOo. 
Broiling, 57, 78. 
Bronchus, 107. 
Burns, Treatment of, 177. 
Butter, 17, 19. 

Callosities, 158. 
Candy, 67, 229. 
Canine teeth, 38. 
Capillaries, 87, 88. 

of lungs, 108. 

of muscles, 153. 
Carbolic acid, 253. 
Carbon dioxide, 104, 113, 115. 
Carpal bones, 125, 152. 
Cartilage, 133. 
Casein, 14. 
Cereals, 21, 67. 
Cerebellum, 191. 

Duties of the, 203. 
Cerebrum, 191. 

Duties of the, 204. 

Hemispheres of the, 192. 
Cheeks, 37. 
Cheese, 19. 
Chest, 109. 
Chicken pox, 241. 
Chilblains, 179. 
Chills and fever, 239. 
Chloral, 182. 
Chocolate, 27, 67. 
Cholera mixture, 254. 
Chyle, 56. 



Chyme, 51. 

Cider, 29. 

Cigarettes, 183. 

Circulation of blood, 80, .89, 

Clavicle, 125, 152. 

Cleanliness, 172. 

Clothing, 176. 

Clotting of blood, 93. 

Cocaine, 182. 

Cocoanuts, 23. 

Coffee, 26. 

Cold-blooded animals, 166. 

Colds, 117, 169, 237. 

Cold, Sensation of, 99, 233. 

Taking, 117, 169. 
Color blindness, 220. 
Concentration of thought, 208. 
Consumption, 20, 117, 240. 
Contagious diseases, 238, 242. 

Immunity from, 241. 

Prevention of, 242. 
Cooking, Purpose of, 72. 

Methods of, 76. 

Principles of, 74. 
Cords, 137, 141. 
Corn, 21, 22, 28. 
Corns, 158. 
Corpuscles of blood, red, 81 ; 

white, 82. 
Corrosive sublimate, 253. 
Cottonseed oil, 17. 
Coughing, 45, 202, 244, 246. 
Cuts, Treatment of, 163, 255. 

Deafness, 224, 226. 
Dermis, 157, 162. 
Diaphragm, 110. 
Digestibility of foods, 56. 
Digestion, 37, 49. 

in the intestines, 55. 

in the mouth, 43. 



INDEX 



267 



Digestion — continued. 

in the stomach, 49. 
Diphtheria, 20, 240. 
Direction of sound, how judged, 

225. 
Diseases, 238. 

Contagious, 238. 

Distribution of, by milk, 20. 

Immunity from, 241. 

Parasitic, 238. 
Dislocation of joints, 140. 
Distance of sound, how judged, 225. 
Distilled liquors, 29. 
Drowning, Treatment in case of, 
120. 

Ear bones, 224. 

drum (see Tympanic cavity). 

Middle, 222. 
Ears, 222. 

Care of, 225. 
Eating, Pleasure in, 68. 

Time of, 60. . 
Eggs, 21, 67. 
Emergencies, 252. 
Epidermis, 157. 

Thickened parts of, 158. 
Epiglottis, 44, 45, 106. 
Epithelium, 60. 
Eustachian tube, 44, 222. 
Excretions, 154. 
Exercise, Need of, 148. 
Expiration, 111. 
Eye, 217. 
Eyeball, 214, 216. 

Size of, 214. 
Eyelashes, 215. 
Eyelids, 215. 
Eyes, Care of, 220. 

Fainting, 95. 



Fat, 17, 153. 

Absorption of, 61. 

cells, 17, 157. 

Digestion of, 56. 
Feeling, 231. 
Femur, 125, 134, 152. 
Fermentation, 27. 
Fermented liquors, 29. 
Fever, Scarlet, 20, 240, 241. 

Typhoid, 20, 240. 

Yellow, 241. 
Finger nails, 161. 
Flavor, Use of, 26. 

produced by bacteria, 240. 

produced by cooking, 72. 
Flour, 21. 
Fly powders, 253. 
Food, Absorption of, 58-62. 

Amount of, needed, 31. 

habits, 65. 

Kind of, 13. 

Mastication of, 42. 

Purposes of, 11. 

Uncooked, as a distributor of 
disease, 245. 

values, 32. 

value tables, 33, 34, 35. 
Foods, Cost of, 32, m. 

Digestibility of, 56. 

for building purposes, 12, 19, 32. 

for fuel, 13, 15, 19, 153. 

Source of, 18. 

Undigested portions of, 62. 
Frostbites, Treatment of, 178. 
Fruits, 23, 67. 
Frying, 58, 78. 

Gall bladder, 47, 54. 
(langlion, 193. 
Gastric juice, 49. 
Gin, 30. 



268 



INDEX 



Glands, 155. 

Ducts, of, 42. 

Gastric, 48, 155. 

Lachrymal, 214. 

of tongue, 227. 

Pancreatic, 54. 

Salivary, 41, 155. 

Sweat, 157, 163, 169. 

Tear, 215. 
Glottis, 44, 45. 
Gluten, 14. 
Graham meal, 21. 
Grape juice, 29. 
Gravity, Effect of, on circulation, 

95. 
Gullet, 45. 

Habits, Acquiring of, 205. 
Hair, 159. 

Tollicle of, 159. 
Health, Disease and, 237. 

Duty of preserving, 249. 
Hearing, Sense of, 222, 224. 
Heart, 82. 

Beating of, 85. 

Center of control of, 191, 203. 

Regulation of, 96. 

Valves of the, 85. 
Hemoglobin, 82. 
Hibernating animals, 167. 
Hinge joints, 134, 137. 
Humerus, 125, 138. 
Hunger, 68, 231. 

Incisors, 38. 

Incus, 222. 

Indian meal, 21. 

Indoor life. Evils of, 117. 

Insects as distributors of disease, 

245. 
Inspiration, 111. 



Intemperance, 72, 250, 
Intestines, 47, 53. 
Involuntary muscles, 143, 145. 

Joints, 134. 

Ball-and-socket, 138. 
Dislocation of, 140. 
Hinge, 134, 137. 
Injuries at, 139. 
Knee, 134. 
Shoulder, 138. 

Kidneys, 155. 

Tubules of the, 156. 

Lachrymal duct, 214. 

gland, 214. 
Lacteals, 62. 
Lard, 17. 

Larynx, 44, 106, 107, 133. 
Laudanum, 181, 254. 
Lead poisoning, 253. 
Lens of eye, 217. 
Lentils, 23. 

Ligaments, 135, 136, 139. 
Lime, 18, 26. 
Liquors, Distilled, 29. 

Fermented, 29. 
Liver, 53. 

Duties of the, 54. 
Lung diseases associated with im- 
pure air, 117. 
Lungs, 106. 

Capacity of. 111. 

Exercise of, 112. 
Lymph vessels, 62. 

Malaria, 239. 
Malleus, 222. 
Malt, 28. 



INDEX 



269 



Meals, Frequency of, (56. 
Measles, 240. 
Meats, 20. 

Cooking of, 73. 

Digestion of, 49. 
Medicines, 237. 
Medulla oblongata, 191. 

Duties of the, 202. 
Mercury poisoning, 263. 
Mesentery, 58. 
Metacarpals, 125, 152. 
Metatarsals, 125, 152. 
Middle ear, 222. 
Milk, 19. 

Curdling of, 51. 

Digestion of, 51. 

Diseases distributed by, 20. 
Mind, Dependence of, on body, 
210. 

Care of the, 207. 
Mineral substances, 26. 
Molars, 38. 
Molasses, 28. 
Morphine, 181. 

Mosquito bites, the cause of 
malaria, 239. 

Treatment of, 255. 
Motor centers. Location of, 206, 
207. 

nerve fibers, 200. 
Mouth, 37. 

-breathing, 105. 
Mumps, 240, 241. 
Muriatic acid poisoning, 253. 
Muscle, Biceps, 141. 

fibers, 142. 

sense, 235. 
Muscles, 141. 

at joints, 137, 139. 

Contraction of, 144, 145. 

Growth of the, 147. 



Muscles — continued. 

Involuntary, 143, 145. 

Number of, 146. 

of blood vessels, 97. 

of breathing, 109. 

of eye, 216. 

Structure of, 141. 
Myosin, 14. 

Nails of fingers and toes, 161. 
Narcotics, 180. 

Effect of, upon mind, 210. 
Nasal cavities, 41, 44, 230. 
Nearsightedness, 219. 
Nerve cells, 195. 

fibers, 145, 194. 

trunks, 194. 
Nerves, 96, 190, 194. 

Anterior root of the, 194. 

Duties of the, 198. 

Motor, 200. 

of hearing, 224. 

of muscles, 145. 

of nose, 230. 

of retina, 218. 

of skin, 157, 162. 

of tongue, 227. 

Posterior root of, 194. 

Sensory, 200. 

Yaso-motor, 99. 
Nervous system, 189. 
Night air, 118. 
Nitric acid poisoning, 253. 
Nitrogenous foods, 14. 
Nuts, 23. 

Oatmeal, 21, 67. 
Oats, 21, 22. 
CT]sophagus, 44, 45. 
Oil glands, 160. 
Olfactory nerve, 2;>0. 



270 



INDEX 



Olive oil, 17. 
Opium, 181, 254. 
Optic nerve, 216, 218. 
Organic matter, 18. 
Overindulgence, 72, 250. 
Oxalic acid poisoning, 253. 
Oxidation, 104, 153. 
Oxygen, 13, 104, 113, 115, 116. 
Use of, 114. 

Pain sense, 234. 
Palate, 37, 44. 
Pancreas, 47, 54, 156. 
Papillae of hair, 159. 

of tongue, 227. 
Paragoric, 181, 254. 
Parasites, 73. 
Parasitic animals, 239. 

bacteria, 239. 

diseases, 238. 
Paris green, 253. 
Peanuts, 23. 
Peas, 23. 

Pelvic girdle, 125. 
Piano, Learning to play the, 203. 
Plumbing, Importance of, 243. 
Pneumonia, 117. 
Poisoning, Treatment for, 252. 
Pores of skin, 164. 
Potatoes, 23, 32. 

Cooking of, 73. 
Pressure, Sense of, 231. 
Proteids, 14, 153. 

Absorption of, 61. 

coagulated by heat, 74. 

Digestion of, 50, 55. 

Need of, 50, 55. 

Source of, 33, 34, 35. 
Pulmonary artery, 84. 
Pulse, 86. 
Pupil of the eye, 217. 



Radius, 125, 152. 
Recreation, 209. 
Reflex action in spinal cord, 201. 

in medulla, 202. 
Rennet, 51. 
Repair of body, 12. 
Respiration, 105, 115. 

Restoration of, 120. 
Retina, 217. 

Ribs, 125, 127, 133, 152. 
Rice, 21, 22. 
Roasting, 57, 77. 
Rubbing, 174, 237. 
Rum, 30. 
Rye, 21. 

Saliva, Use of, 41, 43. 
Salivary glands, 41, 155. 
Salt, 26. 
Sauces, 229. 
Scapula, 125, 138, 152. 
Scarlet fever, 20, 240, 241. 
Secretions, 154. 
Sensations, 213. 

Location of, in brain, 199, 
207. 
Sense organs, 214. 
Senses, 213, 231. 
Sensory nerve fibers, 200. 
Sewage, 243. 
Shoes, 131. 
Shoulder joint, 138. 
Sight, Sense of, 214. 
Skeleton, 124, 125. 
Skin, 156. 

Care of, 172. 

Functions of, 163. 

Sensations of, 231. 

Structure of, 156. 
Skull, 127. 
Sleep, 207. 



INDEX 



271 



Smallpox, 241. 

Smell, Sense of, 214, 229. 

Duration of, 231. 

Location of, 230. 

Use of, 230. 
Snake bites, Treatment of, 254. 
Soothing sirup, 181, 254. 
Sore throat, 46. 

Sound, Direction of, how judged, 
225. 

Distance of, how judged, 225. 

{See Hearing.) 
Soups, 75. 
Special senses, 214. 
Spinal cord, 126, 192, 201. 

Duties of, 200. 

Gray matter of, 193. 

White matter of, 193. 
Spine {see Backbone). 
Sprain, 140. 
Stapes, 222. 
Starch, 15. 

Absorption of, 61. 

Digestion of, 43, 55. 
Sternum, 125, 127. 
Stews, 75. 

Stimulants, 149, 180. 
Stimulus, 145. 
Stings, Treatment of, 255. 
Stomach, Structure of, 46. 

Digestion in, 49. 
Strychnine poisoning, 254. 
Sugar, 16, 28, 153. 

Absorption of, 61. 
Sulphuric acid poisoning, 253. 
Swallowing, 46. 

Center of, 191, 203. 
Sweat, 163. 

glands, 157, 163, 169. 
Sweating as a heat regulator, 
168. 



Taking cold, 117, 169. 
Tallow, 17. 
Tapeworm, 239. 
Tarsal bones, 125, 152. 
Taste, 214, 226. 

buds, 227. 

Confusion of. With smell, 
228. 

Duration of, 228. 
Tastes, Different kinds of, 227. 
Tea, 26. 

Tear glands, 215. 
Teeth, 37, 38. 

Care of the, 39. 

Growth of, 38. 

Milk, 38. 

Permanent, 38. 
Temperature of body, 13, 167. 

Eegulation of, 165, 168. 

Sense of, 233. 
Tendon, 137, 141. 
Thinking, Location of, in brain, 

207. 
Thirst, 68, 231. 
Thorax, 109. 
Throat, 44. 

Sore, 46. 
Tibia, 125, 134, 152. 
Tinfoil poisoning, 253. 
Tissues, 88. 
Tobacco, 86, 182. 

Use of, 182. 
Toe nails, 161. 
Tongue, 37, 44, 226. 
Tonsilitis, 41. 
Tonsils, 40, 44. 
Touch, Sense of, 213, 231. 
Trachea, 45, 106, 107. 
Trichina, 239. 
Tuberculosis, 20. 
Tubules of kidney, 156. 



272 



INDEX 



Tympanic cavity, 223. 

membrane, 223. 
Typhoid fever, 20, 240. 

Ulna, 125, 152. 
Urea, 154. 
Ureter, 156. 
Uvula, 37. 

Vaccination, 241. 
Yaso-motor nerves, 99. 

Center of, 191, 
Vegetables, 23. 
Veins, 83, 88. 
Venous blood, 115. 
Ventilation, 116, 118. 
Ventricles, 83. 
Vermiform appendix, 47. 
Villi, 59. 

Duties of, 61. 

Structure of, 60. 
Vertebrae, 126. 
Vertebrates, 126. 



Vocal cords, 106. 
Vomiting, 47, 252. 

Warm-blooded animals, 166. 
Warmth, Feeling of, 99, 233. 
Warts, 159. 

Waste products, 54, 63, 153. 
Water, 24, 25. 

Absorption of, 61. 

Impurities in, 25. 

Loss of, through lungs, 114. 

of lakes, 25. 

of reservoirs, 25. 

of rivers, 26, 243. 

of springs, 25. 

of wells, 25. 
Wheat, 21, 22. 
Whisky, 30. 
Whooping cough, 240. 
Windpipe, 44, 45, 106. 
Wounds, Treatment of, 255. 

Yeast, 27, 78. 
Yellow fever, 241, 



MAY 27 1903 



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